You are mistaken if you think that the fuse cannot be the problem. I hate to tell you how intermittent problems I've been through over the years that were fuse related. In a case such as this, you always eliminate the obvious possibilities first. As other have advised, replace the fuse, don't just look at it and think that it looks OK. I've seen fuses read good with an Ohm meter, but flake out under load, never assume
Pete