I wasn't able to get download a version of Tinkers Construct that wouldn't crash the server. However, I think I'll just remove Tinkers Construct. Thank you for your help on finding why my server kept crashing
I downloaded a forge file for a server with my friends, did everything you would usually do for a vanilla server, then put the mods in the mods folder. I tried to run the forge universal file in my Server folder, but it would just be open for a little while then closes. This is for 1.12.1
Log: https://pastebin.com/8f3v8xwF