Account Level Reserve with useless support channels

Is anyone else experiencing an extremely high 'reserve' on their account? As in pretty much all of their income from sales is being held in reserve? I don't understand what's happened and the support channels are hopeless. Any guides or policies give generic reasons and don't seem to apply to our situation.

Raised a case on 24th December to query it. This got 'transferred' immediately and as of yet have heard nothing back. Seller support are only able to tell me that once the case gets transferred, it gets a new case ID from the team that are dealing with it -whoever that new team is now? Seller support can no longer see updates or communicate with the team that deal with it. All they can do is escalate the issue if more than 14 working days passes and we don't get an answer.

In the meantime, I've got no visibility of this new case ID, or the progress, so I don't know if this mysterious team are waiting on me or if I'm waiting on them. I can't fathom why there's not even a trace of the new case ID on the 'manage support cases' screen so that we could at least see some sort of progress or expected completion date, or know who's waiting on who. We're just left in the dark day after day hoping for an email to come in.

Issue 1) Why does it take 10+ working days to 'investigate' why the account is on reserve? And who are this elusive team that are working on it, that no-one can get in touch with or communicate with? Why do 'transferred' cases not continue to have a front-facing ID that we can review and communicate through?

Issue 2) What actually is the reserve and how does the amount get calculated? We're currently receiving £0 from all of our sales. As far as I can see the account is in good health and there's been hardly any chargebacks or refunds, etc. Again, very little guidance or communication on what the issue is.

Any moderators on here able to shed some light?