This happens in vanilla

Steps to reproduce:

1 - Spawn a character in GM (works with both USSR and US)
2 - Hold L to turn on flashlight
3 - Tap L and R in quick succession to equip the flashlight and immediately turn it off
4 - Tap R and see the light pointing towards the left

To reset the glitch, just unequip the flashlight while it is still on and equip it again.

(While trying to reproduce this issue's bug, I ran into another bug where equiping and unequiping the flashlight would also turn it on and off. But I don't know how to reproduce this second one)