Delay in opening up timeline with auto transcription / captions.

I'm just trying out the transcription and captions feature (on 15.1 but with the early access).

I've a 30min, multicamera cut sequence with 8 audio tracks. It is transcribed and has had EBU subtitle captions generated.

(When initially generated PP was not playing back the multicam video, restart of the app has fixed that - but maybe if I'd just waited whilst it did whatever caching it needed to do)

I am noticing that, if I insert or delete time in the timeline (thus moving clips and captions left or right to open/close) there is quite a delay whilst that is processed. 

(Also the transcription is not updated to reflect the change - but I understand that might be tricky to implement. )