It's usual for the S&T lee enfields to need work right out the box. So no, you didn't get a lemon, just an S&T!
Sounds very much like the loading fin C clip may have pinged off - when you draw the bolt back, does the fin come with it? Is the C clip in place on top, holding the fin onto the nozzle?
Right out the box, to get it in any way functional, my No. 4 needed the rear of the bolt tightened up with loctite (cocking handle was wobbly), 4 missing screws added (forgotten at the factory to attach the trigger box), a trimmed down airsoft pro L96 AWS loading fin (alloy) + matching airsoft pro C clip adding.
More optionally, adding in a cut down M130/M140 L96 spring, autobot (or similar improved) bucking, and a thrust bearing at the back of the spring guide will improve things too.
Well worth it - it is hands down the most fun rifle that I own to skirmish with.
The fin does move with the bolt, the clip seems attached. Yesterday I had another look at it, I removed the fake “bolt release” and got it to fire BB’s, however it fired 3 at a time about 4 times before it reverted to not firing at all. Upon inspection I couldn’t identify any major flaws. I’m not used to bolt actions at all so completely out my depth here ?
Hmm, very odd then. I presume that it does this no matter how many BBs the mags are filled with? Very important not to overfill the S&T mags - about 25 rds max should be your guide.
Assuming so, I'd return to PB as if it isn't the loading fin/C clip, it possibly indicates something more fundamental with the loading ramp or the hop unit (although really, there isn't much go go wrong on either of those).
The Airsoft Lee Enfield group on facebook is a treasure trove of info - someone on there may be able to help you out.
I've been filling the mags fully, I didn't know it was possible to overfill them however yes it does it regardless of amount of BB's.
It must be something silly but like I said, out of my depth with bolties. Aside from the issues, when it did fire it fired lovely but will definitely look at modifying the next one with a different spring as I heard it has a habit of bunching up and definitely a better fin. I'm assuming the thrust bearing is to do the same thing they do on the AEG spring guides, help the spring rotate and stop it bunching up?