We used a pliers to try to get it off and it broke. I don't think it had to do with build quality.
So it was possibly a user mistake then... that's good news!
So it seems we are back to the flicker on the 650's being the only problem sort of confirmed... sort of cause there is no other experience recorded with these lights.
You might have gotten two bad ones... let's hope for that... (and that you get it fixed easily and at no expense).