TL;DR
Belt building now has the feature to always follow a straight line when holding down the build button. I have an alternative suggestion that fixes the issue this was meant to solve without limiting how you paint down belts.What ?
Instead of forcing a straight line, anchor the mouse pointer in relation to to the game world when the character is holding the build button and is moved in any direction that isn't the direct result of a player input, such as when you hit an electric pole or anything that pushes your trajectory to the side.In other words, Instead of locking the belt to a straight line, move the mouse pointer in the opposite direction when the player trajectory is changed by something else than direct player input.