diff --git a/extensions/include/extensions/multiplayer/protocol.h b/extensions/include/extensions/multiplayer/protocol.h
index 95a0f996..fafc2212 100644
--- a/extensions/include/extensions/multiplayer/protocol.h
+++ b/extensions/include/extensions/multiplayer/protocol.h
@@ -78,6 +78,7 @@ enum LightChangeType : uint8_t {
 
 struct MessageHeader {
 	uint8_t type;
+	uint8_t _pad;
 	uint32_t peerId;
 	uint32_t sequence;
 	uint32_t target;
diff --git a/extensions/src/multiplayer/networkmanager.cpp b/extensions/src/multiplayer/networkmanager.cpp
index 218b05a4..79118a8e 100644
--- a/extensions/src/multiplayer/networkmanager.cpp
+++ b/extensions/src/multiplayer/networkmanager.cpp
@@ -175,7 +175,7 @@ MxResult NetworkManager::Tickle()
 					}
 					else if (IsConnected()) {
 						AnimCancelMsg cancelMsg{};
-						cancelMsg.header = {MSG_ANIM_CANCEL, m_localPeerId, m_sequence++, TARGET_HOST};
+						cancelMsg.header = {MSG_ANIM_CANCEL, 0, m_localPeerId, m_sequence++, TARGET_HOST};
 						SendMessage(cancelMsg);
 					}
 					m_localPendingAnimInterest = -1;
@@ -326,7 +326,7 @@ void NetworkManager::CancelLocalAnimInterest()
 	}
 	else if (IsConnected()) {
 		AnimCancelMsg msg{};
-		msg.header = {MSG_ANIM_CANCEL, m_localPeerId, m_sequence++, TARGET_HOST};
+		msg.header = {MSG_ANIM_CANCEL, 0, m_localPeerId, m_sequence++, TARGET_HOST};
 		SendMessage(msg);
 	}
 
@@ -638,7 +638,7 @@ void NetworkManager::ProcessPendingRequests()
 			}
 			else if (IsConnected()) {
 				AnimInterestMsg msg{};
-				msg.header = {MSG_ANIM_INTEREST, m_localPeerId, m_sequence++, TARGET_HOST};
+				msg.header = {MSG_ANIM_INTEREST, 0, m_localPeerId, m_sequence++, TARGET_HOST};
 				msg.animIndex = animIndex;
 				ThirdPersonCamera::Controller* animCam = GetCamera();
 				msg.displayActorIndex = animCam ? animCam->GetDisplayActorIndex() : 0;
@@ -715,7 +715,7 @@ void NetworkManager::BroadcastLocalState()
 	}
 
 	PlayerStateMsg msg{};
-	msg.header = {MSG_STATE, m_localPeerId, m_sequence++, TARGET_BROADCAST};
+	msg.header = {MSG_STATE, 0, m_localPeerId, m_sequence++, TARGET_BROADCAST};
 	msg.actorId = actorId;
 	msg.worldId = inRestrictedArea ? WORLD_NOT_VISIBLE : (int8_t) currentWorld->GetWorldId();
 	msg.vehicleType = DetectVehicleType(userActor);
@@ -1066,7 +1066,7 @@ void NetworkManager::SendEmote(uint8_t p_emoteId)
 	cam->TriggerEmote(p_emoteId);
 
 	EmoteMsg msg{};
-	msg.header = {MSG_EMOTE, m_localPeerId, m_sequence++, TARGET_BROADCAST};
+	msg.header = {MSG_EMOTE, 0, m_localPeerId, m_sequence++, TARGET_BROADCAST};
 	msg.emoteId = p_emoteId;
 	SendMessage(msg);
 }
@@ -1201,7 +1201,7 @@ bool NetworkManager::IsClonedCharacter(const char* p_name) const
 void NetworkManager::SendCustomize(uint32_t p_targetPeerId, uint8_t p_changeType, uint8_t p_partIndex)
 {
 	CustomizeMsg msg{};
-	msg.header = {MSG_CUSTOMIZE, m_localPeerId, m_sequence++, TARGET_BROADCAST_ALL};
+	msg.header = {MSG_CUSTOMIZE, 0, m_localPeerId, m_sequence++, TARGET_BROADCAST_ALL};
 	msg.targetPeerId = p_targetPeerId;
 	msg.changeType = p_changeType;
 	msg.partIndex = p_partIndex;
@@ -1664,7 +1664,7 @@ void NetworkManager::HandleAnimStartLocally(uint16_t p_animIndex, bool p_localIn
 AnimUpdateMsg NetworkManager::BuildAnimUpdateMsg(uint16_t p_animIndex, uint32_t p_target)
 {
 	AnimUpdateMsg msg{};
-	msg.header = {MSG_ANIM_UPDATE, m_localPeerId, m_sequence++, p_target};
+	msg.header = {MSG_ANIM_UPDATE, 0, m_localPeerId, m_sequence++, p_target};
 	msg.animIndex = p_animIndex;
 
 	const Animation::AnimSession* session = m_animSessionHost.FindSession(p_animIndex);
@@ -1699,7 +1699,7 @@ void NetworkManager::SendAnimUpdateToPlayer(uint16_t p_animIndex, uint32_t p_tar
 void NetworkManager::BroadcastAnimStart(uint16_t p_animIndex)
 {
 	AnimStartMsg msg{};
-	msg.header = {MSG_ANIM_START, m_localPeerId, m_sequence++, TARGET_BROADCAST};
+	msg.header = {MSG_ANIM_START, 0, m_localPeerId, m_sequence++, TARGET_BROADCAST};
 	msg.animIndex = p_animIndex;
 	SendMessage(msg);
 
@@ -1720,7 +1720,7 @@ void NetworkManager::BroadcastAnimComplete(uint16_t p_animIndex)
 	}
 
 	AnimCompleteMsg msg{};
-	msg.header = {MSG_ANIM_COMPLETE, m_localPeerId, m_sequence++, TARGET_BROADCAST};
+	msg.header = {MSG_ANIM_COMPLETE, 0, m_localPeerId, m_sequence++, TARGET_BROADCAST};
 	msg.eventId = (static_cast<uint64_t>(SDL_rand_bits()) << 32) | static_cast<uint64_t>(SDL_rand_bits());
 	msg.objectId = animInfo->m_objectId;
 	msg.participantCount = 0;
diff --git a/extensions/src/multiplayer/server/protocol.ts b/extensions/src/multiplayer/server/protocol.ts
index 33c89638..cbc2d976 100644
--- a/extensions/src/multiplayer/server/protocol.ts
+++ b/extensions/src/multiplayer/server/protocol.ts
@@ -1,10 +1,10 @@
 // Protocol constants — must stay in sync with protocol.h
 
-// MessageHeader binary layout: type(1) + peerId(4) + sequence(4) + target(4) = 13 bytes
-export const HEADER_SIZE = 13;
-export const PEER_ID_OFFSET = 1;
-export const SEQUENCE_OFFSET = 5;
-export const TARGET_OFFSET = 9;
+// MessageHeader binary layout: type(1) + _pad(1) + peerId(4) + sequence(4) + target(4) = 14 bytes
+export const HEADER_SIZE = 14;
+export const PEER_ID_OFFSET = 2;
+export const SEQUENCE_OFFSET = 6;
+export const TARGET_OFFSET = 10;
 
 // Routing target constants
 export const TARGET_BROADCAST = 0;
@@ -19,7 +19,7 @@ export const MSG_ASSIGN_ID = 0xff;
 // AssignIdMsg: compact server-only message — type(1) + peerId(4)
 const ASSIGN_ID_SIZE = 1 + 4;
 
-// HostAssignMsg: header(13) + hostPeerId(4)
+// HostAssignMsg: header(14) + hostPeerId(4)
 const HOST_ASSIGN_SIZE = HEADER_SIZE + 4;
 
 export function createAssignIdMsg(peerId: number): ArrayBuffer {
diff --git a/extensions/src/multiplayer/worldstatesync.cpp b/extensions/src/multiplayer/worldstatesync.cpp
index 2ac22ff2..54c73118 100644
--- a/extensions/src/multiplayer/worldstatesync.cpp
+++ b/extensions/src/multiplayer/worldstatesync.cpp
@@ -237,7 +237,7 @@ MxBool WorldStateSync::HandleSkyLightMutation(uint8_t p_entityType, uint8_t p_ch
 void WorldStateSync::SendSnapshotRequest()
 {
 	RequestSnapshotMsg msg{};
-	msg.header = {MSG_REQUEST_SNAPSHOT, m_localPeerId, m_sequence++, TARGET_HOST};
+	msg.header = {MSG_REQUEST_SNAPSHOT, 0, m_localPeerId, m_sequence++, TARGET_HOST};
 	SendMessage(msg);
 
 	m_snapshotRequested = true;
@@ -275,7 +275,7 @@ void WorldStateSync::SendWorldSnapshot(uint32_t p_targetPeerId)
 	stateBuffer[dataLength++] = (uint8_t) lightPos;
 
 	WorldSnapshotMsg msg{};
-	msg.header = {MSG_WORLD_SNAPSHOT, m_localPeerId, m_sequence++, p_targetPeerId};
+	msg.header = {MSG_WORLD_SNAPSHOT, 0, m_localPeerId, m_sequence++, p_targetPeerId};
 	msg.dataLength = (uint16_t) dataLength;
 
 	std::vector<uint8_t> msgBuf(sizeof(WorldSnapshotMsg) + dataLength);
@@ -288,7 +288,7 @@ void WorldStateSync::SendWorldSnapshot(uint32_t p_targetPeerId)
 void WorldStateSync::BroadcastWorldEvent(uint8_t p_entityType, uint8_t p_changeType, uint8_t p_entityIndex)
 {
 	WorldEventMsg msg{};
-	msg.header = {MSG_WORLD_EVENT, m_localPeerId, m_sequence++, TARGET_BROADCAST};
+	msg.header = {MSG_WORLD_EVENT, 0, m_localPeerId, m_sequence++, TARGET_BROADCAST};
 	msg.entityType = p_entityType;
 	msg.changeType = p_changeType;
 	msg.entityIndex = p_entityIndex;
@@ -298,7 +298,7 @@ void WorldStateSync::BroadcastWorldEvent(uint8_t p_entityType, uint8_t p_changeT
 void WorldStateSync::SendWorldEventRequest(uint8_t p_entityType, uint8_t p_changeType, uint8_t p_entityIndex)
 {
 	WorldEventRequestMsg msg{};
-	msg.header = {MSG_WORLD_EVENT_REQUEST, m_localPeerId, m_sequence++, TARGET_HOST};
+	msg.header = {MSG_WORLD_EVENT_REQUEST, 0, m_localPeerId, m_sequence++, TARGET_HOST};
 	msg.entityType = p_entityType;
 	msg.changeType = p_changeType;
 	msg.entityIndex = p_entityIndex;
diff --git a/extensions/src/thirdpersoncamera/controller.cpp b/extensions/src/thirdpersoncamera/controller.cpp
index 1e715c95..369fd013 100644
--- a/extensions/src/thirdpersoncamera/controller.cpp
+++ b/extensions/src/thirdpersoncamera/controller.cpp
@@ -105,6 +105,16 @@ void Controller::OnActorEnter(IslePathActor* p_actor)
 		return;
 	}
 
+	// Stop external animation before modifying ride/display state —
+	// the ScenePlayer may hold a reference to the ride vehicle ROI.
+	if (m_animPlaying) {
+		if (m_animStopCallback) {
+			m_animStopCallback();
+		}
+		m_animPlaying = false;
+		m_animStopCallback = nullptr;
+	}
+
 	LegoROI* newROI = userActor->GetROI();
 	if (!newROI) {
 		return;
@@ -157,6 +167,16 @@ void Controller::OnActorExit(IslePathActor* p_actor)
 		return;
 	}
 
+	// Stop external animation before clearing ride animation state —
+	// the ScenePlayer may hold a reference to the ride vehicle ROI.
+	if (m_animPlaying) {
+		if (m_animStopCallback) {
+			m_animStopCallback();
+		}
+		m_animPlaying = false;
+		m_animStopCallback = nullptr;
+	}
+
 	if (m_animator.GetCurrentVehicleType() != VEHICLE_NONE) {
 		m_animator.ClearRideAnimation();
 		m_animator.ClearAll();