My dome lights flicker most times I attempt to turn them on. They almost never seem to turn on completely, unless a door is open, and seem not to go off completely sometimes when I turn them off.

Anyone ever see this issue or have a clue what might be going on?

 

Did someone install LED bulbs in there?

Your issue is probably the switch inside is not making/constantly making slight contact.

 

LED's will do that.

The neutral / standby / middle switch supplies low current so they're never completely off (parasitic drain) .

To turn them off completely, turn the switch to off.