I run a private direwolf20 server, running modpack version 1.1.1.
For the past 10 days, the server has been fine. When I checked it today, it was down. When I remove all the mods and boot into a test world, everything is fine. Here are the error logs/crash reports:
Endertech and Thermal Dynamics not playing nice? Probably the only way to fix it is to open the map in MC Edit and delete the offending items, or being drastic, the entire chunk if you can't figure out what exactly is causing the problem. Since it's a stack overflow, there doesn't appear to be an entity involved where you could turn on the forge option to delete erroring entities, at least I don't think that will help. It looks like the super conductor is sending energy and receiving energy from a tesseract and it loops until it dies? Something like that anyway. Ask your players who might have a setup like that, and see if you can find it in MC Edit. The problem with MC Edit is it doesn't display mod items like that (at least last time I checked) so everything will be purple blocks and you have to try to find the exact one to delete by reading the data values of all the blocks in the area until you find the right one. That can be tricky, so going nuclear and deleting the whole chunk might be the only way. You can also try loading the world in a single player game and see if that works, you can get an idea of where the problem is, and use MC Edit then to find the bad connector.