Too many snapshot files when S3 is not avaliable

[SychDan]

When S3 is not avaliable in runtime, snapshot files is not deleted.
On fail, cleanup() method is invoked. This method deletes deltas, reverseDeltas, but not snapshot, because snapshot publishing is not completed
So when S3 is not available a long time, unused snapshots take up a lot of disk space.
Do you have a some workaround for this bug?
Is it a bug or feature?