Put the summary of the bug you're having here

What I expected to happen was...:
I expected it to happen as it always has until today. I launch my first instance, no problem. what i expected to happen was that on my attempt to launch a second instance, it would pop up with the "Already joined the game as this user" warning as usual. I would then proceed to press the "Start anyway" and would expect a second instance to open, so i could play on two worlds simultaneously.

What actually happened was...:
First instance started fine, no problem. Second instance popped up with the usual "Already joined game as this user" Box as expected, but after pressing "Start anyway" it loaded for a second, then popped up with 
Unable to extract native files.
Error details: Minizip error while extracting: -111
Filename on disk: lwjgl-3.2.2-natives-windows.jar
Path: C:\Users\kaspe\AppData\Roaming\.minecraft\libraries\org\lwjgl\lwjgl\3.2.2\lwjgl-3.2.2-natives-windows.jar
Exists: File
**

I looked in the file location, and the mentioned file was there, as expected. Attempted deleting the file, but to no avail. As soon as i attempt to run the second instance, the file reappears, and error occurs

Steps to Reproduce:
1. Open legacy launcher and run an instance
2. When first instance is ready, open legacy launcher again
3. Attempt to run a second instance, and press "Start anyway" to pop up box.