I know it's not my mouse because I had the exact same problem with New Vegas until I installed the unofficial patch. It only happens with this game now and when I'll be holding Right Click to aim down the sights, he will randomly just go back to hip firing. It usually happens right after I shoot, but sometimes I can't even look through my scope at all.

Any ideas?

Anyone?

Still encountering this bug. Tried two other mice - one of which was brand new - and it still happens.

It happens with me as well.

IT is especially annoying when using sniper rifle and anything with scopes. In my case it seemst o happen far more often with scoped weapons.

I too thought perhaps it was a mechanial button issue on my Logitech G600 mouse.

But that is not the case.

It is some glitch in game.

Going to bump this again for awareness. Hopefully someone down the Bethesda pipeline will see this and it might get fixed soon. I can't count the number of times I lined up a shot with my sniper rifle only to have my gun stop aiming down the sights and I shoot in their general direction which alerted everyone. I love stealthy long-range characters in Fallout games and this pretty much has ruined my favorite gameplay style.

I've experienced this myself. The only way I've found to correct the issue is to switch to another weapon with a scope, aim, let go then switch back to the weapon I want to use.