The problem:
These doors are animated. However when passengers sit in the carriages the doors do not replicate until they stand up (excluding the middle coach)
The doors replicate for the driver but not for the passengers
(Animations with AnimationController)
Could you include some of your code that deals with the doors directly? Aswell as a GIF or something to show the issue? 
My train runs on a modular system so… I’ll post the code which is run when the driving player pushes the door keybinds
(The driver would have network ownership)
function module.DoorTrigger(door)
if Train.ActiveSeat.Value then
if door == "Left" then
door = Train.ActiveSeat.Value.Parent.Name == "Front" and "Left" or "Right"
elseif door == "Right" then
door = Train.ActiveSeat.Value.Parent.Name == "Front" and "Right" or "Left"
end
end
if door == "Left" then
if LICFlag == true then return nil end
LICFlag = true
local L = not LOpen
if L == true then
LOpen = true
--Open Behaviour
Train.Front.Cabin.InterlockLight.Material = "SmoothPlastic"
Train.Rear.Cabin.InterlockLight.Material = "SmoothPlastic"
Train.Front.Cabin.Speedometer.Screen.Drive.LDOpen.BackgroundColor3 = Color3.new(1,0,0)
Train.Rear.Cabin.Speedometer.Screen.Drive.RDOpen.BackgroundColor3 = Color3.new(1,0,0)
for _,v in pairs(LeftDoors) do
spawn(function()
v.Model.DoorRootMain.ChimeUnlock:Play()
wait(.25)
v.Model.DoorRootMain.UnlockActivate:Play()
v.OpenAnim:Play()
end)
end
else
--Close Behaviour
for _,v in pairs(LeftDoors) do
spawn(function()
v.Model.DoorRootMain.ChimeLock:Play()
wait(1)
v.CloseAnim:Play()
v.HoldAnim:Stop()
wait(1.25)
v.Model.DoorRootMain.LockActivate:Play()
end)
end
end
wait(3)
LOpen = L
if ROpen == false and LOpen == false then
Train.Front.Cabin.InterlockLight.Material = "Neon"
Train.Rear.Cabin.InterlockLight.Material = "Neon"
end
if LOpen == false then
Train.Front.Cabin.Speedometer.Screen.Drive.LDOpen.BackgroundColor3 = Color3.new(0,1,0)
Train.Rear.Cabin.Speedometer.Screen.Drive.RDOpen.BackgroundColor3 = Color3.new(0,1,0)
end
LICFlag = false
elseif door == "Right" then
if RICFlag == true then return nil end
RICFlag = true
local R = not ROpen
if R == true then
ROpen = true
--Open Behaviour
Train.Front.Cabin.InterlockLight.Material = "SmoothPlastic"
Train.Rear.Cabin.InterlockLight.Material = "SmoothPlastic"
Train.Front.Cabin.Speedometer.Screen.Drive.RDOpen.BackgroundColor3 = Color3.new(1,0,0)
Train.Rear.Cabin.Speedometer.Screen.Drive.LDOpen.BackgroundColor3 = Color3.new(1,0,0)
for _,v in pairs(RightDoors) do
spawn(function()
v.Model.DoorRootMain.ChimeUnlock:Play()
wait(.25)
v.Model.DoorRootMain.UnlockActivate:Play()
v.OpenAnim:Play()
end)
end
else
--Close Behaviour
for _,v in pairs(RightDoors) do
spawn(function()
v.Model.DoorRootMain.ChimeLock:Play()
wait(1)
v.CloseAnim:Play()
v.HoldAnim:Stop()
wait(1.25)
v.Model.DoorRootMain.LockActivate:Play()
end)
end
end
wait(3)
ROpen = R
if ROpen == false and LOpen == false then
Train.Front.Cabin.InterlockLight.Material = "Neon"
Train.Rear.Cabin.InterlockLight.Material = "Neon"
end
if ROpen == false then
Train.Front.Cabin.Speedometer.Screen.Drive.RDOpen.BackgroundColor3 = Color3.new(0,1,0)
Train.Rear.Cabin.Speedometer.Screen.Drive.LDOpen.BackgroundColor3 = Color3.new(0,1,0)
end
RICFlag = false
end
end```Hm it is pretty weird, Maybe it’s the method in which you are animating the doors, Why not just use TweenService to move then smoothly for all clients?
Incase that could be the fix:
Passengers meaning players? If that is the case and your doors are not anchored, then set the network ownership of the root of the doors (or the entire train assembly). There’s most likely a confliction with network ownership more than anything.
[UPDATE]
Found that the problem seems to affect rigs attached to an assembley
Animations dont play if there is a rig sitting in that assembley (and does not have network ownership)