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When removing the sticker from the bed earlier today, I came to the startling conclusion that the glass plate was loose...
this led me to and idea;

I autocallibrated the bed as usual, then identified the low and high spots and used shims under the glass plate (layers of A4 paper) to ever so slightly tune the bed,
This seemed to work, I then tried to autolevel/calibrate the bed again, excpecting it to be janky after. It was! Only with a very random pattern of low and high spots... The previous pattern was somehwat logical with low spots starting at the Z tower leading up to high spots at the Y tower, pretty much in a straight line between the towers.

Then I deduced the BLTouch probably is rekt, but I needed this printer working ASAP.
So what I did is that I replaced the 6 M5's, which bolt the bed down with longer bolts and the spacers with sturdy springs so I could at least get it to print whilst leveling the bed manually, even though this really is an emergency fix...

This worked, but I figured I'd autocallibrate the bed and see if I could get a better 'random' pattern saved in the EEPROM, because the current pattern was hard to tune, even with 6 adjustment points.
When doing this however, the nozzle crashed into the buildplate.

The buildplate has risen roughly 8mm in relation to the old set-up, I measured the old set-up with aluminium spacers these measured around 12mm give or take 0.1mm. The new distance being somewhere close to 20mm.

Can anybody explain why this happens? Because when I run a print it just works normally.. No crash..
I do use a G30 command at the start of each print instead of a G29, is G29 somehow different besides the number of probing points?
I am using the original stock smoothieware that came with the printer originally by the way.

For now the machine is useable, but I really want to find an adequate solution to this...

Below is the start G-code for the printer, which I got from a lovely contributer 2 years ago;
G28 ;Home
G92 E0
M280 PS3
G28 ; home all axes
G1 Z50 F25000 ; lift nozzle
G30 Z0.975; my nozzle height - the higher the value, the smaller the distance from nozzle to bed
M280 S7 ; Lift BL Sensor