Odd brake/tail light problem

Take a length of elec wire, strip each end, use vice-grip or similar and clamp one end to trunk lock striker.
Take the other bare end, and touch it to the "socket or bulbs base" of the offending lights.
If they begin to act as they should, repair the grounds as nec.
There may be a ground screw(s) on the inside lower edge of the trunk, where the harnes lays.

As it is now, I believe you'll find, the park lite electricity is going to the bulb, but can't ground, so juice goes back up the brighter brake filiment (both filiment are likely lit) up to ground the circuit thru the indicator bulb in the dash that is also lit .
Good luck .