Inconsistency between amount of pending transactions and invariants

Observed on an isolated mirror while performing a flood scenario. producer=broadcaster had around 1000 occurrences of that alert:

2022-07-01T14:05:32.642831 block_producer.cpp:199        apply_pending_transa ] Postponed 12906 transactions during block production (0 failed/expired)
2022-07-01T14:05:32.910965 db_with.hpp:165               ~pending_transaction ] Postponed 6787 pending transactions. 6119 were applied. 0 expired.
2022-07-01T14:05:32.910991 database.hpp:850              check_invariants_cou ] NOTIFYALERT! inconsistency between amount of pending transactions 12906 and invariants 12904