The mining server is currently hosted at Hetzner. For a while they had 40% packetloss on parts of their network. Not sure if it was a bad router or another customer being DDoSed.
They seemed to have fixed the issue now though. 0% packetloss.
Update: Hetzner confirms it was a DDoS against another customer on the same subnet.
hetzner's responses to DDoS own