I’ve just published update Z21-1506C that fixes a problem in the vector support introduced in Z21-1505F. We were using an incorrect flag bit in one of our vector support checks. Oops! That causes a S0C7-FE abend to pop up when starting a debugging session for a SRB.
If you have Z21-1505F installed and have been seeing random S0C7-FE pop, please install this fix as soon as possible.