Using ForceCustom Mode causes TPose for single frame in Level Sequencer

We are seeing TPose issues when swapping between EDL shots on skeletal mesh actors.

We have spawned skeletal mesh actors added to a Level sequence that are set to use an animation blue prints which do not work correctly within the Level Sequence, for this reason we use the 'Force Custom Mode' flag to disable the use of the ABP. This works fine except the first frame of each Level sequence shot is always in the TPose.

It is easier to see if you setup a cutscene with a skeletal mesh actor/ animation with Force Custom Mode set to true then create a Master cutscene using a shot track to change between 2 shots that both ref the Level sequence containing the skeletal mesh actor. If you then click on the time line of the master Level sequence from one shot to the other you will see the actor is in the tpose, any subsequent click in the same shot results in the skeletal pose being evaluated correctly.

Using a Master custsene with Multiple tracks allows easier reproduction of the issue because shot tracks seem to fully reinitialise the Level sequence when changing shots (Itself not being a very good thing to do, re-spawns every thing, is slow etc etc)

Steps to Reproduce

Create a Level sequence containing aa actor with skeletal animation. Add a basic ABP to the actor and set the animation to use the ABP. Set Force Custom Mode on the animation. Save the Level sequence

Create a second 'Master' level sequence. Add shot track and add 2 shots that are within the playback range of skeletal animation. Set each shot to use the Skeletal Mesh Level sequence as the subsequence.

Click between shots, you should see that the first time you click to the alternate shot the actor will be in the TPose.