Yildiz SPZ 20b - Sticking Trigger

[Pippin89]

Hi All. I have the above shotgun. The missus uses it more than me, but both of us have encountered the trigger sticking back after the first shot. I can see a witness mark in the trigger guard where, I am pretty sure, the trigger is getting caught. I took some fine grit sandpaper to the guard to knock off any burr that was catching it and that seemed to fix it for a handful of shots but soon started again.
I was going to be a bit more aggressive with the sand paper but thought I would check here first.

My first question is, should the trigger be going back as far as to contact the guard in the first place.
And my second question (based on the answer to the first) is how would you solve it.

[Pippin89]

Bump... Does anyone have any insight on this?