Sometime the tail lights stop working. When this happens .y turn signals flash very fast but very dim. Sometimes the light on the radio will flash with the signals. Hazards are fine but sometimes also dim. Then the next day it will be working fine until the next time. Sometimes it works for a week or two Sometimes it happens later the same day. Mostly at night. Once everything was OK with key on engine off headlights on but soon as I started the vehicle it the problem came back stayed for a day then after sitting for a day it’s fine again
Look for corroded grounds and corroded bulb sockets. On a vehicle this old bad ground are always a go-to failure point.
I had very similar problems with my '74 Volvo when it was only a few months old, and it turned out to be multiple bad ground connections. If that could happen to a badly-designed new car after just a few months, imagine how many bad ground connections there could be on a vehicle that is more than 2 decades old.