I had zero luck with the crimped fittings. After the 3rd one started to leak, I switched to Aeroquip EZ Clip system. The hose is almost half the OD and it's a a simple squeeze of a plier type tool to lock the clamps. You can assemble everything, adjust all the fitting clockings and then click all the clamps, done. Fittings are reusable.
Common problem is the hose and fittings need to match. If you are using the correct hose and fittings they will not leak. I will bet I have done close to 100 with zero failures.
