it carries-up and locks in place. But when doing a very slow and deliberate double action, it's HORRIBLY difficult for me to get it to advance and lock and hold -- before dropping the hammer.
As long as it will carry up and lock at normal speed, it's okay.
And how often do you operate it in a very slow and deliberate speed?
Test it again with empty cases in the chambers. It'll probably speed it up a bit.