I don't know if there's an easy way to fix them. When our DVD-ROM drive stopped working completely a few months ago after intermittent problems for some weeks, we just bought a new one. I don't think it was very expensive, certainly less than £20. In your place, I'd buy new drives. If you need to, you could start a new thread asking for advice on the best ones to get. I forgot to say this before, but welcome to WU!
Madeline.
-------------------- "Power tends to corrupt, and absolute power corrupts absolutely." Lord Acton, 1887.