Error was in customized user exit SARPRFUX showing as
S0C4 in SARPRFUX+038C
the abend occurred because of register R7 got corrupted - from the error information you can see it was hex zeros at the time of abend. The instruction at offset +388 in your user exit code expects R7 to contain the address of PRF control block, which it tries to modify, but fails as the resulting incorrect address points to low core storage.
Generally, to get this corrected, you need to ensure that when the MVI instruction at offset +388 is executed, R7 contains a valid address of PRF control block. You may need to use a different register to store your ACEE address, or save your PRF address into different register and reload it to R7 before executing the MVI instruction that experienced the abend.