I don't recommend cleaning the board with anything other than compressed air and an appropriate electronics cleaner. You will do more damage than just age oxidation and dust if you use gas or water and detergent. I don't know about naphtha as a good choice. It's better to do a search for approved products.
For the purposes of identifying the cause of your issue, I don't think you need anything other than compressed air. Removing the various components, blowing the debris from the contacts, and reinserting the component, several times, will serve the purpose of checking the electrical contacts.
Motherboard faulty bad capacitor repair Punj Tips and Tricks - Electronic Tips
What are the BIOS LEDs and audio beeps indicating?
Regards