Anomalies with OVH and GRE tunnel.?

Question

GRE

Generally. So I decided to connect protection to Hetznery through VPS OVH. I bought a server, made a tunnel. Everything seemed to be going well, but when the attack began, there was a total kabzdets. Losses became more than 30%, everything hung, flew out, it was sad. For a month I tried to understand what the problem was, until I tried to check the loss without a tunnel. And what do you think - there are no losses.

That is, under the same conditions through the GRE tunnel, there is a loss of 30%+, through a simple TCP connection there is no loss. I tried to set up an IPIP tunnel, it's still more fun, when you turn on OVH protection, it simply drops all incoming packets.
(Of course, I have added all the necessary IPs to the whitelist of the OVH firewall, this is not the problem)

Does anyone know how to try to solve the situation? I assume that OpenVPN can solve the problem, because there the packets do not go through tunneling, but simply through the Internet, but still I want to get to the bottom of the truth and fix the GRE tunnel.
Thanks in advance for any information