I've determined that the binding is with the cam inside the E61, not with the wheel brew switch. I have still only backflushed with water, no detergent. The binding can be significant at times, ie require a bit of force to overcome, and non-existent at other times.
Please advise, it seems strange that I would have to pull the lever/cam to lubricate with a brand new machine that has never seen detergent backflush.
I wonder if this was present at manufacture testing in Italy, or the bench test at 1st-line. I do have a couple deep scratches one of the big nuts where the lever shaft enters the group, not sure if someone had it off for some reason.
Every unit gets bench tested here with water at 1st-line - we check for normal operation testing the grouphead, how water and steam valves, and proper refilling of the boilers. We check for potential leaks as well as any damage that may have occurred in shipping to us or within our warehosue.
The lever gets pulled up at least 3x. Since the grouphead is mechanical, it would seem that the binding would happen every time. However, I woulkd never rule out a possibility of it being sporadic.
On other models of machines, it has been the brew switch that I seen this intermittent problem. In addition to too much detergent, I have also seen some water types that strip the lubricant from the grouphead internals. As for finish on the nuts, I have seen every brand with some scratches as these are all placed in a bin to hit each other while shipping to a manufacturer. I have complained about this to all manufacturers with e61s. (added via edit). Please email me a picture of the scratch and I will follow it up with Lelit.
First, I would backflush with a small amount of detergent. Test for a few days. Not backflushing with detergent may be causing the sporadic issue.
Second, if not already done so.... With machine powered off,I would pull the lever up and down many times with the brew switch taped in. Try to replicate the binding as this is the only way to rule out the switch which is more likely then the cam. If you can not bind the grouphead, then it points to the switch behind the lever.
Third, if you can bind it with the switch taped in, I can send you some lubricant.
Again, the e61 group is mechanical and if there is an issue inside, it is usually not a sporadic problem from what I have experienced in the last 21 years. I will also ask the engineer at Lelit regarding your issue.