Belt would be the first thing i would change.
I recently fitted a new one on my 320d and that did this so changed it again and all ok now.
Both belts where good brands Dayco was the first and replaced with Gates.

Mine just stopped like yours.
Easier job than on the e46 i had to change only about 10 minutes.

Also did you use the new "O" rings.
Some don't change them and get this problem.

A failing hard drive has been mentioned but everything works as it should.
Sandisk was one i tried re formatted them all fast and slow.

g48 by Coma is the same stuff.

Normally there is one at the header/expansion tank.

Tried usb 2 and an older one along with several brands of usb 2 all fail at the same point.
I gave up after around 6 goes at it.

My car is a 2010 with the cic but it won't update.
Plug the usb stick in and it starts updating but fails at 56%.
Tried many sticks but the same every time.

As above but look at the wires going to the injectors.
I had something very like this and it was one wire had rubbed on the steel injector pipe ever so slightly.

Where they new injectors as i had this same problem and needed 2 injectors.
Cam-sensor didn't see that in your list sometimes don't show a code.

I fitted LED's to my mains 5 years ago but nothing said at mot time.

Was thinking of re-gassing the new to us 320d but i would jinx this good weather lol.
Might just do it on Saturday morning as i get free use of the machine at my old m8's garage as long as i do it myself.

Mine is cold that cold i turn it off sometimes for a short time as i feel i need my coat on lol.

How long has it been using that amount.
The undertray will hold a lot before it drips.

Tyres.
You say fronts relatively new what tread is on the rears.