So I'm looking at a parent's Magnavox zv420mw8 VCR/DVDr combo machine which hasn't worked properly in years by just...

I actually solved the issue and half fixed the unit. There was a clear plastic pillar piece that was broken on the VCR side that sat over a tiny bulb hidden underneath it. Replacing that piece allowed the unit to keep running with power and the DVD side functions normally now. VCR side remains dead, but she just wanted to be able to finalize her DVDs.