Branches are marked as deleted when an error occurs during change detection.

Consider the following flow:

DefaultChangeDetectionManager#collectChangesWithRetry
  DefaultChangeDetectionManager#handleRepositoryExceptionForDeletedBranchWithRetry
    DefaultChangeDetectionManager#handleRepositoryExceptionForDeletedBranch
      ChainBranchManagerImpl#handleVcsBranchDeletedOfPlanBranch

This is how exception thrown during change detection will lead to branch being marked as deleted.
Then branch expiry could remove such branch.

Possible ways to fix it

• make smarter decision when marking branch as deleted
• make BranchDeletionService verify such branches and reopen them?

Workaround

Disable deletion on branch expiry configuration for a plan.