I've seen glass fuses where the flat conductor inside has physically broken away from the end cap from vibration, build quality, etc.
The result is a fuse that looks ok to the eye, and SOMETIMES still has a connection intermittently. The weak connection that passes the meter test may not allow enough current flow for real life operation...
1938 Canadian Pontiac Business Coupe (aka a 1938 Chevy Coupe with Pontiac shaped front sheet metal - almost all Chevy!)
1975 4-speed L82 Vette