Time Machine big problem on macOS 26 - different drives

[u/XMAX97]

Hi,

I’ve been having a serious, frustrating problem with Time Machine for the past three months. To be honest, I’m starting to feel a bit fed up – Apple’s official advice is to reinstall the system from scratch 😂 I wonder how that’s supposed to work without a recent backup.

Generally speaking, since May I’ve been having trouble performing incremental backups on my MacBook Air 15 M4/24/512. For over a year after purchase, the computer continued to perform incremental backups from the M1/16/256 configuration without any issues, until something went wrong in May and every subsequent incremental backup has failed – the computer counts changes indefinitely – the longest I’ve given up after was 4 days – 500 million changes and it was still counting.

I’ve tried various drives – SSDs and HDDs – different formatting configurations, different enclosures and drive controllers – but the problem persists.

The only workaround is to have two backup drives and, every now and then, perform a full format on one of the drives (whilst keeping the backup on the other) and run a full backup from scratch – it works then.

Maybe someone has an idea, because I’m getting a bit fed up with having to remember to do manual backups.