Something like this can often by corrected by a shim behind the cartridge guide, which closes the gap at the rear where the rim of the case gets lifted up through the guides, making the rim of the case lift higher, so that the nose of the shell doesnt face plant into the top of the chamber and jam up.
The right hand cartridge guide is more accessable. Unscrew the right hand cartridge guide screw(screw above the loading gate on the outside) and the cartridge guide will come lose on the inside of the action, (Just a strip of metal with a groove in it) you can then wiggle it out.
Put a thin folded strip of aluminum from a beer can where the guide fits into (without covering the screwhole) and then fit the cartridge guide back over the top and screw it in.
Try working a few cartridges through the action and see if it has improved.
