Those guns are the A1 model, well known as not being reliable. The new mags are actually made in Germany by H&K, I've got two of them, in fact they're probably the only two in Canada and no I'm not selling them!
I'm constantly amazed at the amount of SA80 crap I've collected over the years even though I don't really like the SA80 that much. From a rested position with the magazine on the ground it can be accurate, but the trigger pull is awful and made worse by successive fiddling with it.
I had an L85A1 of my own before they were banned in the UK, the original trigger was crap but the second version which was thicker (back to front) was much better and it worked. Then there were complaints about use in the artic, ice would build up behind the trigger, so they redesigned it again, and that version is crap, IMO. It has an angled back to cut through ice, but the curve in the trigger is too high up and you can't get enough leverage on it, which is really important with the long trigger bar on a bullpup.
Hardly anyone uses the SA80 in the artic, mostly only UKSF goes up there and they all have Diemacos so I could never see the issue myself. I'm sure there was a better fix.
The mag release thing was also a fiasco, with the glue on guard that fell off. Then they redesigned it, put in a stronger spring and made it flatter and now it is really hard to operate. Personally I much preferred the original design, it was positive and it did work, the real solution I think was to make the end of the button larger and flatter, so it was still easy to operate, but they just made it flatter and now it's too fiddly. In that video you see the soldier having difficulty seating the magazine - that's because the mag catch spring is too strong.
Only the FA MAS G2 is harder to reload. That's a four letter word starting with "C" and ending in "T".