I've noticed that when i click to use slithers poison spray it will sometimes go in the complete opposite direction. Does not happen often but has happened often enough and i have tested it to make sure it wasnt just me messing up. Sometimes it happened with behemoth too.
As you use it if you move or turn around, it will go the way you turned. Ie.
your running away and want to slow then down if you use it and try to keep running it might mess up, so really yeah it is you.