Sounds like you've got a gremlin on your hands unique to what prior owner may have done or an unrelated mystery - generally not fun.
That said, auto electrical troubleshooting isn't rocket science. It DOES require a systematic, logical approach, the right basic tools, and plenty of patience.
If you want to do it yourself, I recommend a YouTube search for "auto electrical troubleshooting" and checking out ones with the highest view counts - there's some great instruction out there.
OR, if you have more money than time (or limited patience like me
look up reviews for a local auto electrical specialist - they can be more affordable than you'd expect and save you lots of swearing/headache. Just make sure to describe the problem well, ask about labor rate and try to get a ballpark for what the issue might be. Mom once paid <$200 to repair two brake lights were out on an an old Subaru when I didn't have time to do anything beyond check the fuses - potentially worth it when factoring time your time and cost of trial-and-error part replacement.
Best of luck!
Portland-based and on the hunt for a well-maintained Gen 1 in Washington, Oregon, or California - I'd consider flying as far as Texas for the right car. DM me if you know of a sprightly specimen looking for a good home...