Enfield No2 MkI cylinder problem

My Enfield's cylinder is having difficulty turning for each shot.
The lever that is supposed to push the cylinder to it's next position usually withdraws into the frame, instead of pushing out and up. I've tried fixing it with a miniature elastic band, pulling it forward, but this has limited success.
It also seems as if the back end of the cartridges are sometimes getting stuck, not allowing proper rotation. I've tried a bit of gun oil, but again, I've had limited success.
This is not the pre-assembled one, but the model version that I built myself.
Any suggestions?
Brock