session recording freezes UI (but still running in BG)

hi, I have 2 app which I'm experimenting on session recording. Both sees this issue.

Under some circumstances (I know how which and how to replicate) the watch UI will freeze during session.start()

Eg:
Go to custom app
Press start (session.start()) - within this session.start I also call UI.requestupdate
Watch UI will freeze. The timer time or elapse time will not increment.
Press start again to do a session.stop(). Watch UI will update the screen and I will see dist/timer time etc updated.
Press start again and session.start will start again, watch UI freezes.

This happens also with Travis.vitek recorder app as well (To be frank. I was happy cos then it's not only my bad coding practice. Lol...)

Can someone take a look at it?

Oh.. When this freeze happens, I just need to exit and discard the session and get into it again and then all will be good again.