Chupp4Jo3

Have you tried the /gamemode normal and have you given yourself operator status on the server?

I assume you use localhost or your server systems IPV4 address? Also next time it happens try posting the server and your client logs, it might say something. (Also check allocated RAM on the client on the off chance that is your issue)

try reinstalling the server and if the issue persists see if there's a crash report then post that and/or the ENTIRE log file. remember to try and use pastebin or something similar as it makes it a lot easier to look through.

It something to with Thermal Foundation (as it quite clearly says at the end of line 35 net.minecraftforge.fml.common.LoaderExceptionModCrash: Caught exception from Thermal Foundation (thermalfoundation) Look at their GitHub issues page to see if the problem has been addressed and if not open an issue with them and, if necessary, ask the pack author for help.

Also it looks to me like you have a crash report hinted at in the log you posted. Check for that and upload it to pastebin as well.

Hey there @SomeoneAwesome, I see you have not read the EAQ. All large text stuff (like logs and crash reports) need to be uploaded using something like Pastebin. If you just plain text paste them here the text looks a mess and is even harder to look through.

Are you putting your IP in the 'Server IP' bit of the server.properties file? If so DON'T! This is if the server is being run on one machine but 'hosted' on a machine with a different IP (Don't ask me I don't get this stuff) leave it blank and (if you're on the same network) use your local IP (if unsure type ipconfig into a command prompt window and look for ipv4 address)

Also check how much RAM twitch is allocating. Go to the 3 lines in the upper left corner > settings > minecraft > Java settings and check the maximum allocated memory. Also check that the instance doesn't have it's own RAM allocation set too low.

Most mods also include the MC version in the mods file name (e.g. base-1.12.2-3.10.0.jar) try and filter those out while looking in the mods folder of you're instance and that will help you get through the list quicker. Also I'd check GalacticCraft purely because of the last line before the error says about that injection error but I know jack about Java so...

He means max RAM I guess, In the Twitch client click on the vertical ellipses and go to profile options then make sure 'use system settings' is unchecked and then you can adjust the slider to allocate RAM. Alternatively you can enable advanced settings in launch options on the new MC client or the edit options button on the bottom left of the old client and change the -Xmx<'insert numbers here'>m numbers to 5120m for 5 gig of RAM or 6144m for 6 gig. Hope this helps!

Also check if the client get's a crash report. I have had this issue recently where I would get a weird wheat recipe registration issue when I joined my server and the server logs didn't tell me anything but it turned out the client generated a crash report even though both the server and client never closed

If you had to guess which one would you think? I'll just try disabling mods until something sticks in the meantime. TY for the response though!

*bump*

I don't think an addons folder is standard. I assume the mod you mention adds one itself. Most 'addons' for mods in forge are forge mods themselves (eg. Extra Cells 2, the like 8 thaumcraft addons that got updated 5 minutes after Thaumcraft was, Immersive Integration etc.)

1.7.10 is no longer supported on the forums sorry dude. however my guess would be a lack of resources, have you tried dedicating more RAM to the server?