When trying to enter a tape into an IBM ATL or VTS,the CBRUXENT exit may reject the entry and indicate that the tape is a foreign tape when it is not. The TMC is correctly updated even though the tape is rejected.
Check the SYSLOG for the message IEFTMS9 BACKUP REQUIRED, AUDIT FILE UTILIZATION IS CURRENTLY xx%. If the audit file has reached the threshold that you set in the options for CA 1 (THAUDT) then CBRUXENT will treat the insert as a foreign tape. Run TMSCOPY and then retry the entry of the tape.