A premature explosion could result from a damaged or defective fuse. During war time production quality control may not always be what it should be.
The easiest way to damage a fuse is during loading, by missing the chamber and hitting the fuse on the breach ring. This happened once on a gun I was commanding. Needless to say we did not fire that round but packed it up and marked it “N/S damaged fuse”.
In the book “An Awesome Silence” by Eldon Davis there is an account of a 25 pdr gun crew killed (I think from 3Fd RCA) when a shell exploded as the loader threw the shell towards the chamber hitting the breach. The shell shouldn’t have exploded, but it did, so it must have being a defective fuse.
https://www.amazon.ca/awesome-silenc...wesome+Silence