Entering fullscreen causes the player to look in a different direction

[Radk6]

Using LWJGL3ify 2.1.1 and UniMixins 0.1.17 on Prism Launcher 8.4

fml-client-latest.log: https://mclo.gs/V1wf6UN
latest.log: https://mclo.gs/DsWYrWw

Windowed (854x480):

Fullscreen (2560x1440):

It's also worth noting that after entering fullscreen, moving the mouse will immediately "reset" where the player is looking (ie. in the same direction as windowed mode)