My first question here is what firmware you’re running on the easy and rdv4 ?
Latest fw is Iceman/master/v4.16717
if you’re using anything older, I would strongly suggest to update the fw to latest.
Here is the repo, also having pretty good docu of everything you may need for the process
I need to take down the biochip lf antenna off my rdv4 and check with the dual antenna how it behaves with my xmagic implant. I will report back tomorrow
p.s. what if you try with another mifare tag/card ? Does the same behaviour repeats ?