This was a part of the build which I was dreading.
I needed to cut a 50mm diameter hole through the boiler wrapper and the domed end plate, and the bronze join in order to insert the vertical cylinder which houses the cylinder, piston etc..
A series of photos is probably the best method of explaining the process…
And…. thanks to Stuart T, my CNC mill is again in action. Stuart identified the probable culprit component (a chip on a board for the encoder for the Z axis servo motor), made a new board for the new chip and installed it. He was not confident that it would fix the problem, with the likelihood that a complete electronic rebuild of all electronic components would be needed. But it worked! Hooray!! I feel like my right hand has been repaired. Thanks Stuart.