Leon Mk2 2006 - Part of fuse box randomly loses voltage

[Pirulax]

Hello,
I'm a newbie in car electric, but otherwise familiar with electronics.

After trying to investigate some battery draining issue, I've now got problems with basically a row of the (inside) fuse box, namely f27 (fuel pump/relay) and f28 (convenience controls module) not getting voltage (all other fuses are have 12v on them)
Now, obviously since f27 doesn't get voltage I can't start the car.
Interestingly, after some fiddling (disconnecting the battery, or re-seating relay no100 in the engine fuse box) it has voltage again, but then (even while driving) its randomly lost.

I've found a wiring diagram for the car but no clue how to read it (to find out whenever there's maybe some kind of a relay in-between that became fauly due to me unplugging fuses while trying to figure out whats draining the battery)

Ive not yet read the codes out, as I don't have anything to do it with, but I assume it probably won't be of much help as the car was totally okay before me pulling out the fuses.

(As for the battery draining, I was completely mislead by the "convenience controls module" drawing .3A because the door was open, after closing it the overall current dropped to 0.05A)

 

[Pirulax]

Okay... As it turns out I should've started from the most basic step... checking if all fuses properly pass the voltage
I forgot to tighten back D1 ("Multi-terminal voltage supply “30”. Internal fuse box") on the side fuse box in the engine compartment - This fuse seems to be responsible for that entire row, but all other rows are connected to somewhere else.
So yeah...