Older electronic equipment in general uses electrolytic capacitors that dry out with time (like for 80's and earlier era gear) and hence their circuits start acting flaky, sometimes intermettently at first.
The fix is to buy new capacitors of the right capacity and voltage rating, and replace them to get another 25 years of service out of the device.
This is not a fix for everyone, but for a competent hobbyist, not a big job.
Our stereo receiver got this fix for half an hour to id what was needed, half an hour to shop for the bits, and an hour to solder them in. Parts cost was $8.
I have used this to fix old vivitar enlarger and process timers, and my fujimoto roller processor wash dry module and main pocessor module pc boards as well.