I posted last year about this happening. I have an old one and it started to jamb last year. The locking block would rise up and rub the receiver and create friction so it would not cycle closed for the second shot. I researched he exploded diagrams and found a ball bearing between the bolt and locking block. My buddies SPR453 had this bearing too. My old gun did not.
I call EAA and they said you can't buy it, the old guns did not need it. I was like what? It's machined for this bearing, my locking block is rising up and I don't need it, but the new guns do? We took apart my buddies gun and found the bearing is just a hair larger and a .177 BB, so I added one a BB and it cycles fine and no more jambing. Just an FYI for anyone else that might be having trouble.
It takes a total disassembly of the bolt and firing pin to get it together with the Bearing in there, but it fixed all my problems. So it seems to me, if you have an old one and have any issues, you might want to look into this
You can see the BB down inside between the two parts in the bolt.