On board EQ??

[kmk42019]

What causes the on board EQ and volume knobs to stop in in that "groove" so you know its set flat? What causes those "grooves" to become indistinct(hard to notice)?

 

[Caca de Kick]

They're called 'center detents'.
If you want to find your detents again, just use an allen wrench and take off your knobs. turn the shafts until you find the detents, it should be apperent. Then reinstall your knobs, and all should be good again.