Forge version: 36.1.4
Twilight Forest version: 4.0.426
Link to latest log: https://pastebin.com/7BUxwpse

Steps to reproduce:

1. Edit the common config file to include a custom stalactite to hollow hills, such as one using Eidolon's Lead ore.
2. Save the config file once changes are made.
3. Start up the game with twilight forest installed.
4. Look at the config file again after the game has been restarted and you will see that the config section for custom hollow hill stalagtites has been erased and reset back to it's default. You will also notice that a "BAK" file with the same name has been created next to the main config file.

What I expected to happen:
The config file to maintain the custom stalactites added to it.

What happened instead:
The Section of the common config file related to custom hollow hill stalactites gets reset to default every time you start up the game. This makes this section of the config essentially unusable as changes keep getting erased.

Note: This does not happen with any other part of the config, just the part related to hollow hill stalactites. Every other part of the config files works correctly.