SL9 issue +/- SS issue

Hi,
I couldn't find anyone with a similar issue but I apologize if this has been addressed in prior posts:
My SL9 build (with metal SS) frequently freezes following a fired round: by "freezes" I mean the bolt remains open and the trigger and SS are "stuck" in place. The only remedy I have found is to force the front pin open (which takes some doing) at which point the bolt snaps shut and the rifle will fire again (once the pin is put back into proper position). This seems to happen regardless of whether the SS is in the single shot position or the SS position. Clearly something is binding together preventing the bolt from closing but I'm not sure how to trouble-shoot.

Also, and quite possibly related, I finally ground my buffer mass down enough for the SS to kind of work- the problem I'm having is there is not a positive "stop" for the SS in the middle position and the gun's recoil easily jiggles the SS to the right or left which obviously stops SS firing. (If anyone is interested I ground it to about 13.6mm which seemed to be the right dimension for the lever of the SS to stop grabbing the buffer mass). I generally can fire 2-4 rounds before the SS moves into either single shot mode or true safety mode.

Thanks in advance for Tim or anyone else's feedback.
AW

It's the Upper/BCG sold in the complete SL9 upper kit on HT- The BCG is stamped KAK but I don't see an identifier on the upper itself.
Thanks for the Grey Market Research link- I'll check it out.

Thanks!
AW

Thanks for the reply,
To clarify, it is the cam that is shifting side-to-side into either true safe or single fire position. I suspect I do not have the detent retention screw screwed tightly enough (I don't have the weapon with me at present to check) but I recall I wanted to make sure I didn't over tighten/strip that screw, so likely my bad.

And by "grinding the top of the tail down", you mean grinding parallel to the flat upper surface of the tail to reduce its overall thickness, correct?

Thanks in advance for everyone's help.

undeadchew Great, thank you very much for your help!

Ok, I tightened up the retaining screw for the safety detent and that definitely helped the side-to-side sliding issue, but I'm still troubled by "binding" of the BCG. To recap: whether in single fire or SS mode, the gun will periodically (every 2-10 shots) bind following successfully fired rounds. The BCG is rearward, the trigger and SS are unmoveable (probably because the BCG is in the way), and the charging handle doesn't do anything. Something is applying force vertically (from the perspective of a level weapon position) because I have to punch out the front take down pin which relieves the bind and the bolt snaps shut. I have gingerly ground the superior surface of the SS lever and have ground the BCG buffer mass to about 13.6mm.
The GreyMarketResearch link was a little confusing as there were two pictures that showed very different routing paths (one along the sides of where the SS lever sits, and one more focused on the rear shelf behind the SS lever) and unfortunately is now 404'd.
Does anyone have a picture or description of what exactly should be routed out to facilitate proper function?
Thanks in advance for any advice!