For people with large, frequently edited files, our version history fills up all our storage space. This makes Sync stop syncing.
(Please note that the purge function does not currently clear the version history of large note files. Also, buying Sync Plus only makes the problem worse, as it extends our version history to a year!)
Proposed solution
Allow a mid-tier Sync subscription, which expands our storage but does not extend our version history.
For example, we could pay $6/month for a 5 GB plan (that maybe allows for 2 vaults), but still has only 1 month of version history. This could be an entirely separate tier, or an expansion option within Sync Standard.
Current workaround
The official workaround is to delete and recreate your vault periodically, as a hard reset on your version history.
I imagine it would also work to buy the 100 GB Sync plan.