After upgrade from MK3 to MK3S+ can't get good bed contact
So I recently bought this MK3 second hand. After some fiddling and calibration I got it to run quite decent. I decided to upgrade it to MK3S+ and when I received the package I printed the necessary PETG parts. They were pretty much flawless.
During the upgrade I took the liberty of also removing all the smooth rods for cleaning and replaced all the LM8UU bearings with new ones.
I ran the wizard (and several times since), did the first layer calibration, cleaned the sheets with dishwasher soap and IPA. No matter what I do I can't seem to get consistent adhesion. Two heatbeds came with the printer. A textured one (the default I think) marked TL-21 and a smooth golden one marked PA-11. I got the good results on the textured before the upgrade.
My latest test after the upgrade I did on the smooth one (because I wondered if the coating on the other had somehow been affected - though I can't see how). The final first layer calibration looked quite good (didn't take a picture) with the z value dialed to -1.735 (which is a bit higher than I had it before, but this was where I could place the PINDA and not have it touch the paper).
I printed the Bed level test and I don't really know what to make of this result. Some places are ok, some places have nothing and some places are just mangled.
Filament is missing someplaces - mostly on the right side.
In the top left corner a part has broken off while the rest looks ok.
The same on the top center square.
In the lower left square a missing edge but otherwise ok.
The center looks pretty ok to me.
But all the right squares has problems.
How should I proceed from here?
Is there THE BEST way to dial in the Z offset to completely eliminate that as a problem. Are there test prints that can expose any problems that could explain why it is so hard for me to get proper adhesion after the upgrade?
Another thing I noticed when doing the manual check after reattaching the bed carrier was that my bed is curving upwards in the middle across X ever so slightly. I guess the mesh bed leveling should handle that.