Hp printhead issues

Anyone with an idea or solution...I'd sure appreciate one!

I have an HP all-in-one printer L7820 which needed new printheads.
NEW printheads about $99 each (takes 2; one Bk/y other Magenta/blue)
Re-conditioned print heads $35 for a pair

I have tried several reconditioned print heads.
I put them in...they WORK FINE on the first day - maybe 2.
Then: issue appear stating one print head (blk Y normally) will say there is "a problem with (x) printhead".

I've cleaned the points,
VERY lightly sanded the points, etc.
anything youtube videos suggest along with HPprint head recommendations...

Take out, clean points, re-insert - then the 2nd one has issues, or both have issues....
take out, clean points and reset...in the meantime I have
Unplugged the printer, unplug from wall to reset printer

Replace printheads, plug in....etc
repeat processes several times with one or both printheads..

"issue(s) appears again...

any ideas?
I truely hate thinking about landfills getting printers...so I would prefer to mine operational...let alone the $100 ink in the printer...
even if I can get a new printer for $50, I hope to get this operational and "reuse recycle"

anyone? Idea?
thanks