Having setup a full Control Rig using the new Spawn Controls functions in the Construction Event, bringing the Control Rig into a level and editing a new Level Sequence, on saving a keyed sequence, the controls will snap back to a default position.
On re-opening this sequence, keys and controls animate as expected, but this problem re-occurs on every save. Having to re-open files every save is very frustrating for animators and did not occur in 5.0.3 with normal controls that were not spawned in.
I have checked the Control Rig Class settings, which default to not running Construction Script in sequencer, so my only guess is that this is a bug with the Spawn Controls functions in the Construction Event on Control Rigs.
Obviously, this defeats the purpose of procedurally generating controls if the only alternative is to not use them for sequencer to work.