Some hosting providers will throttle packets in this fashion if they see a high percentage of tiny packets (as many DDoS attacks use this kind of pattern). You might be able to fix this issue by padding 0's to the end up each packet, bumping their size to say 250 bytes or so and see if that helps.

But I would say I'm surprised, as 20 a second is really tiny and should easily fly under the radar, as even up to say 250,000 packets per second of small size isn't a big deal and doesn't even typically get filtered like you are seeing. Major DDoS attacks are usually 1-10 million packets per second. It could be a router/firewall misconfiguration. You could also try another host and see if that helps.