Well, then you went down the wrong rabbit hole, and you need to start climbing your way out of it.
Such as?
You really need to stop using ProcessMessages(), and start using proper code designs. Even if you don't want to use timers/threads, there is always TThread.ForceQueue(), for instance. Anything that allows code flow to return to the main UI message loop naturally will be better than manually pumping the message queue artificially.
Then file a bug report with Embarcadero. But don't litter your code with ProcessMessages() calls just to satisfy the framework. Find other alternatives. Stay away from ProcessMessages() whenever possible. That was true even in the old days of the VCL. More so now in the days of FMX on mobile.