The problem is one byte UDP packets to 185.203.119.83:22126 are being dropped. Two bytes work, so it must be a router/firewall setting somewhere.
FYI Linux commands to test using a remote machine
Sending "r" fails:
echo -n "r" | nc -u -w1 185.203.119.83 22126 | tr -dc "[:alnum:] "
Sending "rr" works:
echo -n "rr" | nc -u -w1 185.203.119.83 22126 | tr -dc "[:alnum:] "