Puzzling first layer - wavy, not straight
I have two i3 Mk3 S, one was factory built, and one bought used - and the used machine has the same set up, configuration, etc as the factory built. Both controlled by their own Raspberry Pi with Octopi running. No problem so far.
However, the 2nd machine always produces a wavy-lined first layer. I have tried all the z recalibrations, swapped the filament sensors (to no effect) double checked all the configs, print exactly the same files on both machines - yet one produces straight lines on the first layer, and the other does not.
wiggly first layer 
Does anyone know what I have missed?
Please run the built-in first layer calibration routine and show us the result *on the print sheet*.
Cheerio,
RE: Puzzling first layer - wavy, not straight
Thanks for responding: I have now reset everything again, and lowered the Pinda sensor, then recalibrated - it worked. I had it higher than it should have been, as a result the nozzle was at -1.7mm. Now I have lowered the Pinda, the nozzle is now at -1mm, and it is delivering a straight first layer - with no wiggles.
It would be better if there were an adjustment mechanism on the Pinda with some indication as to exactly how much one has moved it. The approximate thickness of a credit card is not good, I micrometer measured some handy wire, and found it to be approximately 0.6mm - so I used that. Not very exact, to say that the machine is supposedly capable of measuring levels to within 1/1000 mm.
Thanks guys: solved.