Wiring – Is there ever a reason to fuse the neutral rather then the hot line in a small appliance

This question relates to 120V small appliance wiring in the USA. I repair small motorized appliances called microcentrifuges that are used in laboratories, and specialize in models made by a particular German manufacturer – Eppendorf. One particular model has a single 6A fuse and I always assumed that this fuse was in the "hot" line. However, I had one of these models fail and it tripped the circuit breaker without blowing the fuse. Looking for the fault, I found that one brush holder in the motor had come loose and contacted the motor frame which is connected to the protective ground. Tracing back I found that power coming in from the three wire power cord went to a brown, blue and green/yellow wire internally and that the brown and blue wires went to the main switch (DPST). The yellow/green wire went to the metal case as expected. The blue wire was switched to a black wire and the brown wire to a white wire running to the main circuit board. The black wire led to the fused leg in the circuit board. I read that brown is the color for the hot leg and blue for the neutral in European wiring. To me this means that the hot and neutral crossed at the switch. Of course, this crossing might have been done by someone, like me, who was unfamiliar with the European color code. But every unit of this model I have looked at (tens) is wired the same. I have exchanged the wires on a few units, so that brown is switched to black and blue to white, but am worried that I am missing something. There is actually a spot for a second fuse on the circuit board, but this is always jumped with a wire on the units I see. It is used for units wired for 240V in other countries – two 2.5A fuses instead of the single 6A – according to legend on circuit board. And the power coming in does go through a line conditioner, if this is the right term for the small metal box that the power cord plugs into and has the brown, blue and Yellow/green wires coming out of it, if this might make a difference. To further complicate matters, the model that preceded the one I am discussing here is wired as I would expect with only the hot leg fuse protected.