This is for 1.12.2, forge 2847. I dont know what is a a debug.log, but i can show you what it says in the console when i cant enter
[INFO] [minecraft/NetHandlerLoginServer]: UUID of player Enddani is c7efc47d-b597-4ec8-8aa0-9f3bd8495654
[INFO] [FML]: Client protocol version 2
[INFO] [FML]: Client attempting to join with 38 mods : minecraft@1.12.2,tconstruct@1.12.2-2.10.1.87,wolfarmor@3.4.1.1,ptrmodellib@1.0.4,extendedrenderer@v1.0,dldungeonsjbg@1.13.2,toolbelt@1.9.12,baubles@1.5.2,ironfurnaces@1.3.5,mca@6.1.0,bountifulbaubles@0.0.1,configmod@v1.0,jei@4.14.4.264,orespawn@3.3.1,radixcore@1.12.x-2.2.1,colytra@1.2.0.3,craftstudioapi@1.0.0,roguelike@1.7.2,mantle@1.12-1.3.2.24,spartanshields@1.5.4,mcp@9.42,gravestone@1.0.18,journeymap@1.12.2-5.5.3,FML@8.0.99.99,bookshelf@2.3.590,coroutil@1.12.1-1.1.20,llibrary@1.7.19,spartanweaponry@beta 1.3.8,appleskin@1.0.9,additionalstructures@2.3.1,waila@1.8.26,bibliotheca@1.2.2-1.12.2,bookworm@1.12.2-2.5.1,forge@14.23.5.2847,divinerpg@1.6.4,chococraft@0.9.1.52,eplus@5.0.176,ironchest@1.12.2-7.0.52.837
[INFO] [journeymap]: CLIENT
[INFO] [minecraft/NetHandlerPlayServer]: Enddani lost connection: Disconnected
[INFO] [minecraft/DedicatedServer]: Enddani left the game