Indesign runs extremely slow when coming back to any file older than a few days: Mac

Hi, I've been having a major problem with indesign.

I create a new file, import images, create text boxes etc. It works fine, for hours on end. I save the document, close and reopen and everything is fine.

However if I come back to that same document (and countless others) – say, 3 days to a week or more later – it firstly takes ages to reopen (as if a rcovery document is loading) and then when it has opened – is extremely slow. Even simply hovering over each button in the interface makes the computer really struggle to compute. I understand how a really image-heavy document can cause scrolling through pages to be slow but simply hovering over – say, the magnifying glass tool – should not make the beach ball turn for 10 seconds or more. It's as if indesign is thinking about something else the whole time.

When I've managed to close one of these documents (which also takes an age), Indesign is then still extremely slow until I restart and then is fine – until I try to open one of those older (week-old) files again.

I've uninstalled idesign a few times, cleared the caches, turned off GPU, cleared the preferences many times. I've also run disk utility a few times to see if it's just a disk error – all seems fine and has also started doing it to files stored on external drives.

All other programs seem to run absolutely fine, even when I'm getting solid beachball – all other programs are fine.

I'm using a 2020 Macbook Pro. Is this a new compatablitiy issue caused by Apples new M1 chip transition?

Is there a corrupt font causing this?

The weird thing is that with a freshly created document – everything runs as normal for hours. Why would it crash when I revisit anything older than a few days or so?

Really hope someone can help, it's starting to ruin my workflow.

Thanks!