rudschul, it is difficult to see the wiring in your picture of the lamp kit so I cannot compare it with mine. Mine has heat resistant, braided insulation on the leads and I have not used any other form of protection. In the kit there is a coil of spiral wrap, wire protector but nowhere in the instructions is this mentioned. Maybe someone at Sintratec can comment here?

I have sealed the powder compartments really well but did not remove every trace from the corners, leaving a very small fillet. It does not seem to have had an effect on the platform movement, it has always been a little stiff but smooth.

With the very regular problem in your Z direction, I would suspect a problem with the screw that drops the print area. It is difficult to say because there is no scale but if the regular gaps are the same pitch as the screw threads of the lead screw, it may suggest a link between the two such that every one revolution it may skip steps or make a larger drop due to backlash or problem with the drive. Just a speculation based on many years of CNC machining and leadscrew issues. Just ignore me if I'm way off the mark.

Mike