Has anyone found the solution to these old bikes and their charging issues?
Yes. Fix what you have.
1. Honda never made a Cb500F. Honda made CB550F models and all the rest were K models, 500 and 550.
2. The CB 500 has no brushes. Is has an excited field alternator.
3. There are two repair methods:
a) keep replacing parts until it stops misbehaving.
b) Use test instruments to analyze why the system is not behaving correctly. (Got meter?) First thing, measure battery voltage and report.
4. Do we assume your bike is still in stock configuration, and utilizes all the stock electrical components including bulb wattages?
5. Do we assume you have a DMM and skills to use it?