I install these, and there could be a few things to recommend, 1 being the right size spring. The in-line fuse holders going to the shunt have usually 3 different springs to select from helps hold the fuse in place inside the holder, another issue is perhaps not realizing if you grabbed a 1amp slow or rapid fuse. I have experienced some of those fuse holders that the factory made crimps and solder were just awful from the start. There is usually a certain gauge of wire for the ammeter connection as well. It's possible the shop could have placed an older fuse in there that maybe didn't have as much life left to it. I tend to save anything I can to return back to shop stock, so that could be a possibility as well.
Hope this helps
