readiness status failed

Hello,
after update from 16.0.5 to 16.4.1 status url return failed

curl https://git_url/-/readiness
{"status":"failed","master_check":[{"status":"failed","message":"unexpected Master check result: false"}]}

on request extended status https://git_url/-/readiness?all=1
return {"status":"failed","master_check":[{"status":"failed","message":"unexpected Master check result: false"}],"db_check":[{"status":"ok"}],"cache_check":[{"status":"ok"}],"cluster_shared_state_check":[{"status":"ok"}],"db_load_balancing_check":[{"status":"ok"}],"feature_flag_check":[{"status":"ok"}],"queues_check":[{"status":"ok"}],"queues_metadata_check":[{"status":"ok"}],"pubsub_check":[{"status":"ok"}],"rate_limiting_check":[{"status":"ok"}],"repository_cache_check":[{"status":"ok"}],"sessions_check":[{"status":"ok"}],"shared_state_check":[{"status":"ok"}],"trace_chunks_check":[{"status":"ok"}],"chat_check":[{"status":"ok"}],"workhorse_check":[{"status":"ok"}],"gitaly_check":[{"status":"ok","labels":{"shard":"default"}}]}

All services work ok except master. Gitlab work normally. You can explain why present its error ?

Start by reproducing the /-/readiness and /-/readiness?all=1 requests after upgrading from 16.0.5 to 16.4.1. Compare the failed master_check with the other healthy checks and investigate what the reported “unexpected Master check result: false” means. Done means explaining the master check failure and identifying a verified remedy or required configuration.