Su-Chi not able to mana sink into Mishra's

[Seigebrisbane]

I've tried force stopping combat phase and all the 5-6 internal stops within the combat phase as well, I have a Mishras Factory on board ready to use the mana from Su-Chi (produces 4 colorless when it dies) so that I don't take 4 damage in mana burn but no matter what I do I cant get the game to pause or give me the opportunity to do so, it just instant burns me every time.

Anyway to make this interaction work correctly?