Error when assigning employee to fob.

Hi all,

Apologies if this is in the wrong section. I'm having an issue when trying to assign my employees to a fob. https://prnt.sc/qsh519 (Incase the link doesn't work, the error is;
Index 'swipecard' for table 'employee' would not be unique.
I'm pretty sure this means the sytem thinks an employee is already attached to fob I'm trying to link a staff member to however when I try and use this for to clock/ log in nothing happens.
The EPoS system I'm using is PAR PixelPoint POS Version 11.2
Any help or ideas on how to clear the fobs (even though they present nothing when I try to log in with them) would be fantastic.

Many thanks.