I'm stumped without having it in hand. The bolt assembly is out of spec. and needs to be sorted. That much I can see. I recently had an SMLE come here for barreling and I found the body had been blown up and the rear of the breech ring was physically blown upwards and backwards, (the first I'd ever seen), so that's a possibility as Bruce has said although the physical damage isn't evident on your No.4. A wild *** guess is that your body is just plain worn out beyond repair with the bolt flopping around in the runway but I could be wrong.