Clean Lens Atomstack A6 Pro

Hi, I 'm trying to clean my Atomstack A6 pro laser because I ca’nt get to focus correctly and I think the lens could be dirty, The problem is I 'm watching this video:

but I can’t remove the metal part because there is a metal stop in the top part, that is, when I push to take out the metal piece it doesn’t come out because the air assist part is thicker than the hole; I’ve tried to remove it but I can’t because it’s very tight.

Does anyone know how to remove it?
Thanks a lot in advance.