Users of CA-TSS with a region control acid that has the MRO attribute, they got the CICS error message:
DUMP TITLE=CAS9578E - Product = KO50 PSW = 078D2000 A0FB0B8E Completion Code = 00C4
It reveals a S0C4 in CAKSRVAK+D26
This is corrected by HYPER QO90884. But, in some cases is not possible to apply it or to take it in account quickly.
Then the workaround is to remove the MRO attribute from all CICS region acids:
TSS REMOVE(userid) MRO Userid is the cics region control acid who has the MRO attribute
The client has to re-cycle CICS.