Hi @paulvha
great you figured that out! I am very thankful for your support 
Do I understand that right, that this is a problem in the firmware of the Reader which could only be fixed by a FW update?
This means flash the Attiny using an Arduino; which is complicated but doable as @micropuller suggests in this posting: Qwiic RFID keeps sending tag identifier, even if there is no tag present when quickly changing tags - #16 by micropuller