A very serious issue and claim, I'm aware, however I do have reason to believe it is this serious. Starting off, there does seem to be more reports of this online, one as an example. Figured I'd open an issue in case it's not aware.

The issue

Whenever teleporting to the mining dimension, there's a chance where it appears your player just doesn't spawn in. This may be different for others, but it went like this for me: You load the dimension fine, but you'll load stuck in a block. If you break any blocks, you'll break one block, it doesn't drop, and then you can't break anything else (similar to as if you were in adventure mode). You cannot move or do anything. The player model doesn't load in the world, and in your inventory, it's in a very bugged animation. Attempting to use /spawn will result in the same issue, but now in the overworld. If you relog, close minecraft, etc., you will lose access to that world and its backups in that instance. Attempting to rejoin any world will successfully load world data, then display the status "Joining world", then switch to "Saving game" before quickly crashing the entire game. Congratulations! Your world is now bricked.

Replicating

Quite frankly, I'm not sure how you'd replicate this. All I know is that it happens when switching from the Overworld to the Mining Dimension, and this was confirmed from others as well. I'd often run/jump towards the pad before punching it, so maybe it's momentum based? I did try falling, sprinting, clicking it in different ways, couldn't force it to happen. I'll update if I do find a consistent cause.

Backups don't work, so how to fix?

It's a bit of a pain, but there is a way to get your world back to it's former glory. First, you'll need to download a new instance of ATM8. Open the game for the first time so that all files generate appropriately. Close the game. Then head to your broken instance, and in the root directory, locate a folder called "simplybackups", any worlds you played on will periodically back up here. Locate a backup that happened perhaps an hour before the incident. You will lose some progress, but better than losing the entire playthrough (I lost a lot of base progress, but I at least still have my world back!). Unzip, and drag into your saves folder in the new instance. Back in the old instance, you'll want to grab a few things so the move isn't as noticeable. Grab the "journeymaps" folder, along with "options.txt", and "keys.txt", move them all over into your root directory of the new modpack instance. If asked to override, say yes. This should bring back your waypoints, map data, settings, and most of your keybinds, if you changed any.

While out of the way and a pain, this does appear to be the only way to fix this. Deleting playerdata in the world file will not fix this issue, this issue does something to the instance that permanently keeps you from being able to reopen the world in that instance. What it corrupts I'm not entirely sure.

I showed you my logs, pls respond

Server crash log
Client crash log

Update: Shorthand error is java.lang.NullPointerException: Cannot read field "f_108590_" because "this.f_109059_.f_91074_" is null

Despite being divided into two logs, this was a singleplayer world that has never touched online. It has only had one player (me).
If the full minecraft log is required, let me know and I'll go ahead and upload that too.

Minecraft Version: 1.19.2
Java Version: 17.0.3
Forge Version: 43.2.11
Modpack Version: ATM-8 1.0.19b

Thank you ATM-8 Devs

If there's anything else I can provide that may be assistance, please let me know and I'll do my best to assist you the best I can.