Chevy Equinox fuse by pass?

A friend of mine has a 2012 Chevy Equinox that he tows behind his mh. He installed a fuse bypass switch in it. He was having problems with the ignition switch locking up when he tried to remove the key. It is still under warranty so he took it to a Chevy dealer to be fixed. After working on it three times they determined it was caused by his fuse bypass switch. They removed the switch and replaced the fuse and the ignition worked fine. This didn't sound right to us shade tree mechanics so we plugged in the by pass switch and sure enough the ignition locked up again. We tested the by pass switch with an ohm meter and it is working fine. Has anyone run into this before? Could it be caused by additional resistance in the circuit?