It was (still is, for other VMs I have) netcup.
I think it may be related to the Black Friday offers as all the VMs (especially the cheaper ones) are suffering from the same problem. The performance dropped.
I was staying under the caps.
Maybe they didn't do it on purpose, maybe I have some busy neighbours. It's just because I want to stay on a 4 euros/month VPS, otherwise I have plenty of dedicated hosts to use for this - and there, I can autocap myself if needed 🙂