Single shot loaders are not much help. The mags being touted are better than the standard but I did not find them to be a complete fix.
Because pellet probe ends can be so badly finished ie rough, that they can "hook" a pellet. (That needs to be polished up, smoothed off and gently rounded.)
You first need a partial misfeed, then a recock, or to hold the rifle muzzle up, and bosh, a pellet is inside the breech.
To repeat the problem and the fix.
The front of the breech is completely open- there is no front face.
You need to make a front face, with a hole for the pellet probe that is a clearance but less than 4.4mm. (not as hard as it sounds.
A suitable material is 1mm sheet ABS plastic, available from any model shop. Ideally in black. There is enough material from an A5 sheet for dozens of attempts. This is soft and easily worked, drilled and sanded. You cut out a small piece to be the size of the missing front face of the breech. Drill the centre 4.3mm max at the point where the probe will pass through. The hole need only be big enough for the probe to pass through. If you have it right, this plastic would now go over the probe and press back into the front of the breech, being nearly an interference fit- ie it does not fall out and can initially sit there with friction alone.. Now you can remove it, then araldite a tiny smear round the edges and press it carefully into the front of the breech block. The probe is your guide. Remove any spare araldite, especially on the inside of the breech and let it set.
You now have a sealed breech block, with a closed front. The 4.3 mm max hole permits the probe to move freely but if a pellet is pulled back, it is more than 4.3mm and cannot enter the breech. A fix.