I am used to flying planes with KX-155/155a and/or G430/530. In either
case, your OBS and VOR indicator are separate from the frequency select
unit. Add to this the fact that many panels are set up with the DME
slaved only to the #2NAV, and you have ample room for error. It's just
easy, in those situations where you're dialing through frequencies
quickly, to find yourself following the wrong VOR, or not understanding
why your DME is not doing what you expect.

I recently flew an older Cessna, in which the NAV frequency select was
directly ON the VOR indicator, as was the DME readout. This just seemed
like good ergonomics to me - no way to make a mistake. Who makes these?
Why do we see them so rarely?