An enet package might be much larger than the MTU, then fragmentation is done based on MTU of both peers (server/client).
That would be futile as it won't update the MTU on the side of the peer.
Given the information in this thread so far the issue is not on your end, but you can ofc fix the issue on the other end if it's mtu related by lowering your enet mtu at the cost of possibly making all other connections less efficient at the same time.
Attached a cleaner patch without sanity checks that allows setting mtu in config or via command line, ie. pyrogenesis -conf=network.mtu:1392
Anyway not yet convinced that this is the actual issue, yes might be, but still waiting for the output of the original ping command from @Helicity to confirm.
enet-mtu.patch