for implants on the pm3 easy i used the bottom of the device and not the top of the gold traces themselves.
do hf 14a reader and put the next underneath it and move it round till you get consistent reads
try looping hf search and moving the pm3 each time it doesn’t ready. Sometimes it’s a bit tricky to get the orientation right. And as mentioned previously, the hf antenna is actually on the bottom of pm3.
Super simple and you have probably tried, but sometimes it is easy to overlook the basics.
Have you checked the screws are tight on the board?
Have you disassembled the PM3 and inspected solder joins and components etc?
What are your antenna readings? after boot, do the both display as
Im guessing fimware mismatch has been ruled out, this is a trick one.
I think what he means is, too close for a ISO card may cause issues, so use distance space to try and get a read on the cards, The Glassies dont have this same issue, so you dont need the same kind of seperation.
Personally I find I have to press quite hard on my implant to get a read, and my implants are not deep.
I know you have probably tried most if not all of this stuff, but you never know, something may work.