The relay fills in the blanks, and its blanks are not neutral

A relay holding shared session state has a struct with every field in it. A command that changes one field still produces a full struct on the wire, and the fields you did not set take the relay's default — which for a running/paused flag is almost always false. So an item-change command arrives at every follower carrying "not running", on a session that never paused.

Obey it and the follower loads the new item and stops. This looks like a client bug and is not one:

// adapted — names generalized
// The relay forces "not running" on EVERY item change: protocol default, not a member pausing.
// Carry the session's previous intent across the change; a real pause arrives as its own
// command, with the item unchanged, and is applied normally.
val running = if (itemChanged && !incomingRunning) lastSessionRunning else incomingRunning
lastSessionRunning = running