The gfci won't do anything about lost current on the low voltage side of the transformer.
I would still use a gfci to protect from current lost from the high voltage side even if it's not required.
At this point, it's just speculation that the SWG has anything to do with the stray current.
A thorough investigation needs to be done by a qualified professional.
I would still use a gfci to protect from current lost from the high voltage side even if it's not required.
At this point, it's just speculation that the SWG has anything to do with the stray current.
A thorough investigation needs to be done by a qualified professional.