Team, I see the same issue on 9.12(1)2 ASA in Firepower 2130.
Symptoms : Standby device is showing replication is in progress, after some time (approximately 3 hours) both are trying to become active (split brain), and services are down.
This host: Primary - Active
Active time: 42791387 (sec)
slot 0: FPR-2130 hw/sw rev (49.46/9.12(1)2) status (Up Sys)
Other host: Secondary - Sync Config
Active time: 0 (sec)
slot 0: FPR-2130 hw/sw rev (49.46/9.12(1)2) status (Up Sys)