I recognized that somehow I was still connected to Hypixel after having crashed (with the Message "You logged in from a different location"). You can also notice this when first joining Hypixel, then having a crash (with such a Crash Report) and at last, joining a different Server. The Hypixel chat messages are still being written. Here is a screenshot of this happening:

This might also be related to Osmium (Intro-Dev/Osmium#15).

Other than that, your mod is very helpful and great!

Cool, I'll look into it

Fixed as of 3.4.5