I spend 2 weeks to understand how the sequencer works… and it’s not a full success 
But. you can check some tricks.
First, ensure you have the Realtime rendering in the preview (Ctrl+R)
Try to set the camera cut ending at the same frame than the sequence.
Sometime, having 1 frame or more of camerashot after the sequence’s end, lock my gameplay. Sometime not, and I don’t know why.
If you put a Blueprint character in the sequencer, you have to configure some stuff inside.
If your character is animation graph driven, check all your meshes inside and put them in Custom mode, then put the root in animation graph mode.
In the sequencer, you can add a track on the main character mesh to set the mode in Custom mode (or animation only)
There is also a track to add on each mesh, to add the “preview in Editor” without that, there is a chance your mesh will not be animated at all…
After all this, when the Sequence is finished, in Blueprint, set the actor in AnimationBlueprint mode.
In my project, I recreate a PlaySequence Box, to automatizing all this stuff… and it’s a lot of try and retry. Some flags can drastically change things.