Connection to internet from this ISP was overloaded in the recent days. This might've caused the lag issue.
Requesting help once again. I've got a fresh backup of all player files. If anyone has got a fast PC & connection here, we might just move the server temporarily. Besides it will allow to test where's the problem with 4.77 that caused the crash, if it was mod-related. I will try to run the server on my own PC for a while, but I'll need to reinstall Windows before, and, moreover, when I tried to do this before server couldn't connect to global server from here.