Hey Evens,
if you replace the hand trim router, which is a class II double isolated device, that therefore needs the magnet end of the XYZ touch plate to make the collet and the bit part of an electrical circuit for the probing to work, by a spindle, which has to be properly grounded, you don’t need the magnet end of the XYZ touch plate anymore.
Furthermore, for probing with the XYZ touch plate to continue to function, you must make sure that the other wire is not connected to ground, but to the probe output. It may be that you need to use the other touch plate input pin on the CNC controller to connect your touch plate. See here for explanation.
Welcome to the forum!