LN channels can be force closed automatically due to multiple reasons:
  • Stuck HTLCs and both nodes failing to cooperate
  • Channel backups or LND detecting old states
  • Failure to reach agreement on states
  • Your implementation or your peer having an error
You can see all possible reasons by searching "fail the channel" (BOLTs jargon for force closing and/or forgetting a channel) in the BOLTs repository.