Serious syncing issues effecting my team, we can't work?

I'm part of a team of 20 creatives, we build large product catalogues in InDesign (like Ikea or Argos, lots of product images and text on each page). We have one InDesign file for each catalogue page and a series of folders that contain the image links (due to the amount and the complexity of the folder structure we have to use live links, packaging isn't possible). We each take turns working on an InDesign file to avoid syncing errors.
Due to slow server and VPN speeds while WFH we switched last year to Creative Cloud, there's been a few issues but this latest one is pretty serious, and we may have to cancel our subscription and look elsewhere if it can't be resolved.
For unknown reasons half our team is experiencing syncing issues WITHOUT error messages. Either files appear to sync forever, or the changes they make to files don't show up for others (and vice versa). This is making daily workflow impossible. As a compromise we've had to move back to our incredibly slow server.

We've had IT investigate, we've tried everything recommended in Adobe's FAQs and I've searched this forum for advice but so far there doesn't seem to be a fix. If this was just one user I'd question if something was wrong with their computer or WIFI, but this is 10 users effected at the same time. Is something going wrong Adobe's end? At this point I'm looking at moving everyone to OneDrive because this isn't workable.