If you do not figure this out, I suggest you call PM. They have some pretty good support folks about answering these sorts of questions. They helped me out.
I have the 940M CNC and sometime after I finished a heavy job (steel) where I happened to stall the motor when the machine vertical dropped and took a bigger bite than planned. I finished the work just fine. I even changed tools and made more cuts. However, after a while when I went to take the tool out the tool collet would just spin while I was holding the spline. There was a small set screw up under the collet ring that had sheared, but something was still holding everything together. Anyway, I had to go up from the bottom to get to it. To do so, required a wide spanner wrench, which I had to hobble together, to get the ring off so that I could even see the set screw. Replaced it and all worked again. I think this is different from your problem as my spline was still engaged with the gear box. Nevertheless, the machine keep running and working after the shearing event, but eventually it gave up. By the way, there were two set screws in the hole. The outer one was to hold the inner one from coming loose.
Good luck when you reassemble.
I have the 940M CNC and sometime after I finished a heavy job (steel) where I happened to stall the motor when the machine vertical dropped and took a bigger bite than planned. I finished the work just fine. I even changed tools and made more cuts. However, after a while when I went to take the tool out the tool collet would just spin while I was holding the spline. There was a small set screw up under the collet ring that had sheared, but something was still holding everything together. Anyway, I had to go up from the bottom to get to it. To do so, required a wide spanner wrench, which I had to hobble together, to get the ring off so that I could even see the set screw. Replaced it and all worked again. I think this is different from your problem as my spline was still engaged with the gear box. Nevertheless, the machine keep running and working after the shearing event, but eventually it gave up. By the way, there were two set screws in the hole. The outer one was to hold the inner one from coming loose.
Good luck when you reassemble.