There were issues with quite a lot of things in WW2 where the people who'd invented them could set them up and have them work, but as soon as they had to be set up by someone else there were all sorts of issues. The Haselmeyr bofors mountings, for example. Its basically tech which works, but isn't ready to be rolled out - a very important part of the development process (usually not seen by people not in the trade) is making kit squaddie-proof. They did get them working right after the war (when they had time to do things properly)