In reply to cturner:
Here is another data point and my hypothesis.
Env A contains commercial AXI and AHB VIP sub environments.
I’d better not say whose it is, but it not a problem with Questa.
The commercial AXI and AHB VIP uses the UVM run-time phases.
My homegrown VIP (env B) just uses the simple run_phase().
Perhaps there is some interactions having two parallel sub environment where one uses the run-time phases and one wisely does not(mine).
As reported earlier, I got expected behavior when I removed env B from env A (the one using the run-time phases). When I took env B out of env A and put it directly in env Bench, this left all the run-time phases stuff only in env A. Both env Bench and env B just use run_phase.