mathgc_010 OK, I've looked into this again and found that it's a mixin conflict between the 1.20.1 versions of Wurst and SecurityCraft. These mixins have already been updated on both sides in later Minecraft versions (1.20.5 and up).
Since Minecraft 1.20.1 is over two years old and over 90% of players have moved on from it, that version is unfortunately no longer receiving Wurst updates, so the issue won't be fixed in that version. However, if you update to a newer version of Minecraft (e.g. 1.20.5, 1.20.6, 1.21.1, or any later version), then you'll find that the issue has already been fixed there.
Alternatively, if you insist on staying on Minecraft 1.20.1, you can work around the issue by removing either Wurst or SecurityCraft from your mods folder. You won't be able to use them both in 1.20.1, but choosing one or the other would still work.
Hope this helps!
