i notice this problem ever since the modpack updated to 0.63, it only appear a single time tho, when i click back to the server list, and go to my save file again, it load correctly

I've had this happen at least 3 times as well.

This is only a possibility, but it is possible that the Windows firewall is causing this. After this happened several times, I changed the launcher from the GD launcher to the AT launcher, and after the same problem happened once, Windows displayed a dialogue about the firewall for Java, which I allowed, and the problem stopped.