In regards to Revell kits engineered in the mid-60's, in particular their hot rods, in my opinion it's not a matter of quality control. Speaking as a person that does quality control for a living, their kits were designed with a breakdown of parts to elevate the level of scale fidelity of the parts that as a results makes many of them small and fiddly. As a result it can be challenging to get them assembled cleanly.
Gerald, your build came out great. Thanks for sharing!