I've started 2 servers one in a hosting company and one locally.
I only play with another friend so it's just 2 people in the server.
My current server is on a VM, on a server created with the pterodactyl panel, 10GB of RAM and 8GB or disk. (I though it might be a problem with resources.)
Right now if I set the max-tick-time to 60000 it times out then it restarts, if I set it to -1 it still times out the client connection but it doesn't restart the server.
The world was created with MC 1.15.2 and forge forge-1.15.2-31.2.33 (tried updating to forge-1.15.2-31.2.36 but still no luck)
Here's the debug.log
I've also tried to launch a copy of the world in Single Player, with and without mods, and it gets stuck at 100% when loading the world.
These are the mods in the server, until just yesterday it was working fine but after turning it on this morning it stopped working.