I have a Meteor S Mk3 that is a 3rd gun of mine with latching issues that I was going to break for parts but thought I'd just see if I can solve it (this is the one in another post where I fitted a Parker rimfire silencer for fun) however before I go very far is this amount of float? correct at the piston head, gap must be about 2-3mm at a guess.

As for the latching up the profile of the sear and the piston notch seem fine, might be a trigger install issue? spring fitting does seem fiddly.

https://imgur.com/gallery/i4QwFGu

Also the TG serial suggests Mk 4 (or 3 as an S which it is) but has a Mk 5 articulated cocking link, no matter just wondered why but of the years things get altered of course.