Hi guys,.I just bought a new MXR Univibe and the Depth control is tight and really scratchy as if there is sand paper in the depth pot. And this is new!
As far as cleaning them...+1 to DeoxIt, but bear in mind that you likely need to at least partially disassemble the pedal to get to them to clean. So, if you're not comfortable with doing that...
MXR does tend to jam the knobs down to where the rub the painted surface. Your first description sounded like the pot was faulty do to being overheated at installation.