It's not that mudfish isn't stable, or that the server isn't stable, rather from what I see, the German firewall is adding a lot of latency and there's no way to bypass it, VPN simply does not matter in this case, as all traffic will have to go through it.
The main problem with your decision of moving the server to Frankfurt is that to go there, let's say from Spain, in my case, you have to go first to Paris, like any other french people would do, then to Strasbourg, where you meet all the dead nodes, and then to Frankfurt. The routing is done in this order, Paris -> Strasbourg -> Frankfurt. Like you can see in the screenshot:
TLDR: Spanish players are plagued with connection issues right now, and I'd say that everyone who's routings have to go to Paris will have a tough time connecting to the server with minimal ping spikes.