MK3s made unreliable by FW 3.14 !?  

MK3s made unreliable by FW 3.14 !?

Hi everyone, 

I hope someone could help me getting my Prusa i3 Mk3s to print properly again, Firmware 3.14. changed it into an Ender V3! Waaaaaah!

Here is the sad story: (scroll down for TLDR!)
After having printed around 1000 cases with our prusa mk3s at work, I bought a used one for myself (last August), since I was fed up with my unreliable EnderV3se.
I carried my new printer home and printed a absolutely wonderful flawless cam holder. 

I LOVED IT SO MUCH! FINALLY A RELIABLE 3D-PRINTER!

Then, destiny struck:
I UPDATED TO FIRMWARE 3.14 (this was back in October/November) since then my Prusa seems to channel my old Ender somehow:
Unreliable Prints, and ever changing Z-Axis settings, one day its great, next day no adhesion with the same settings the same file. Whyyyyy? :../

MY LOVE STARTED TO FADE AWAY....... =:-|

I moved the Pinda sensor after the XYZ Calibration caught the paper. (space: one cable tie)
I did SEVERAL XYZ Calibrations with SEVERAL different Firmware Versions and SEVERAL full resets to no avail.
I have even changed the whole Print head (one was provided by the former owner) to no avail.
MY LOVE STARTED TO TURN INTO RESENTMENT.... ):-(
Sometimes it sticks, sometimes not, depending on the mood of the day, worse than my EX. (Yes, I know, really!)
Z-Offset calibration is more than irksome, since it looks scratched (too low) when it sticks, but does not stick properly if it is at the right hight. 
I have cleaned the sheet with Alcohol and Soap to no change.
I installed 3.14.1. and the paper gets caught again!
NOW I COMPLETELY LOST MY WILL TO LIVE.....

What am i doing wrong here?
I don't get it why mine is not printing anything properly but the one at work is sh*tting out cases with "fire and forget", it just works...

I spent months on this, and now looking at any prusa just makes me mad/sad..... (Which is some kind of brand recognition, I guess 😉
I hope there is some advice out there..... the last hope......

TLDR:
Working Printer "disabled" by Firmware Upgrade 3.14
Several Full Resets Done
Several XYZ Calibration done
Paper caught.
Moved Pinda
Changed Printhead
Updated, Downgraded and Updated FW (now 3.14.1)
Paper gets caught again in XYZ,
Cleaned with Alcohol and Soap.
Still no proper adhesion or very sad/bad first layer
Could'nt even install my new MMU, because for what?
I am tired now. 
Please help!

Thanks for your time.
Oli