Just a thought from an engineering perspective. Fuseholders often get very light surface corrosion just while sitting exposed. Usually you can't even see it, it's such a fine layer. They can also collect some dust or small debris from air movement. When you insert a fuse into the holder, it's going to make contact at a small point, and that contact point is no longer exposed to oxygen and dust, protecting it for the life of the fuse (normally).
Moving a fuse by pushing it in slightly, depending on the holder design, can actually change the contact point in the holder by a small amount, enough that the fuse is then contacting a lightly corroded spot. It can also drag/push fine dust particles into the contact area.
Whenever I have to reseat a fuse in a fuse holder, no matter how old the equipment is, I always remove it completely and re-insert, and if I see any slight corrosion, dust, or foreign material on it, I wipe it clean and maybe even reseat it a few times to "clean" the contact point in the fuseholder.
If I suspect a fuse contact of causing a problem, I'll even use a fine burnishing tool on the fuse and the contact to clean them.
Usually once a fuse is well-seated, it's going to make good contact for a decade or more unless you have extreme conditions - heavy corrosion, liquids and especially oils can eventually ruin the contact junction.
Anyway, I would urge everyone to completely remove and reseat any fuse you find loose, at least once. And fuses don't need to be pressed in hard, just enough that they're fully inserted into the holder - bottomed out. Once you've done that, you can normally eliminate the fuse box as the problem.
