I run 10 minecraft PE servers using Multicraft and PocketMine for linux which has recently been updated to run on PHP7. Everything works fine on 7 of the servers I updated, but 3 of them will not allow any UDP connections (despite starting and seemingly running correctly), however the same servers when configured to use PHP5 start working perfectly.

I'm running CentOS7 CLI on a dedicated server, and have tried reconfiguring and disabling firewalld to no avail. If I change the port of a broken server to that of a working server everything starts working... so I'm wondering why the switch to use PHP7 causes connections on these ports to fail. I've run netstat etc to see if anything is interfering, but everything looks identical whether they are running PHP5 or PHP7.

The only pattern I can see is that those that don't work are the three highest ports:

Ports that allow connections on PHP5 and PHP7: 19132, 19133, 17171, 20000, 25252, 11111, 12321, 23456

Ports working with PHP5 but not working with PHP7: 33333, 55555, 41414

Any ideas what is going on? Thanks