Time Machine not thinning old backups TimeMachine is not removing any old backups.
The disk itself is plenty big enough (1TB, backing up a 500GB main drive), and I have (multiple times) reformatted it to start TimeMachine afresh. After about a month, the TimeMachine disk is full. I last formatted the disk August 19th, and now (September 10th) the disk is full. I can see about 490 backup snapshots, give or take every hour.
The TimeMachine disk is an SSD, formatted Mac OS Extended &amp; Encrypted.
What could be causing this and what else could I try to get TimeMachine to thin out backups as it used to?
I gave up trying to fix this directly, but after upgrading to macOS 11, and using the same SSD freshly formatted with APFS - as now supported in macOS 11 - TimeMachine is back to working as it should, with hourly snapshots being cleared out after 24hrs.
I can't say if the upgrade cleared out something corrupted, or if macOS 11 can now deal with the issue I was having, but it did fix things.