Welcome aboard!
Great advice above!
Great advice above!
I've written to Rockwell requesting a replacement handle.In that case contact Rockwell and they will probably send you a new handle. The cap post will not last long if you continue with that razor.
It has been established in post #16 the handle is defective and has not been drilled and threaded deep enough.My solution... just give the head a secondary "nip up", once I feel it start to slacken. As I don't remove the blade between every shave, this will hold firm until I intentionally loosen the head, either for a periodic clean and flip of the blade, or to install a fresh one.
So personally, I don't consider this a razor fault.
The OP said; "As to the depth of threading in the handle as compared with the threaded post, the latter is about 6 turns deep, but the former is about 4 turns deep. I used a toothpick, not a match stick."
Six threads is the minimum I would expect for adequate thread length as that equates to only ~ 5mm of threading contact. Using a washer will reduce that thread length contact.