Welcome to the SeeMeCNC Community

I have an FSR setup, but are using the oldstyle original arms, skates an effector mounts (no ball joints or magnets or anything). Probing works fine, an I get repeatable probes if I run them after eachother. Yesterday I was probing in the same conditions as the day before, but I get a difference of up to 0.1 mm that varies greatly from tower to tower. I used the same temp for bed and hotend. That's half a layer and thus far too much. So it looks like cooling down and heating up again makes a difference. Also I think I see some bed bulging after heating up (center seems a little bit higher after warming up.) To get all even I have to do endstopscrew tweaking again. Mind that I did not dismount the bed in the meantime. Is that strange or something to get used to? Now while probing I can measure these thing much better then before

Also I see some tilt when the nozzle hits the bed. There is play in the hinges that connect the arms to the effector, and probably the skates too. When the arm closest to the tower seems to have more play, and the effector is visibly tilting a bit. That can't be good! Will the newer ball cups arms better this? If so, I will have something to add to my birthday-present list.

One more question: Which option is better to countermeasure the probing flex? There is a "Z_PROBE_HEIGHT" and a "Z_PROBE_SURFACE_THICKNESS" (the last one I am not sure out of the top of my head, I am not at home...).

My experience with the new ball joints is very favorable and will eliminate that slop. Also keep in mind that a printer as large as the Max and fabricated with melamine is going to change dimensions with temperature and humidity changes. I can tell when humidity increases during the day based on first layer changes. That's why I calibrate on Duet fairly frequently. My first layers are more critical than most other users so they have to be spot on.

Yes, I think melamine is far from ideal. I see some of te verticals in the base are falling apart. For work on the PSU I had to open up the base a few times, and that certainly does not help keeping everything sturdy. No wonder a lot of members are interested in all metal frames. I am interested too, but would like to finally be able to say I can print nicely on my Max as it is. I am really falling from one problem into another, and have to do with only a few hours per week to be able to work on it. If I ever going all-metal, it wil probably be a custom one from the ground up with all nice upgrades I learned about here. That way I can keep one working printer, but I will have to convince my wife first