Did you resolve this? Same thing is happening to my Superb Estate. From your diagram, it would appear that the tension spring is missing in mine, but haven't found a broken one in the boot.

Similar issue with the larger hatch glass panel not opening. Have applied Greenliner1's approach with pasting a soft tab, it worked and connected with the switch to give the 'all door locked' brake flash. I want a more permanent solution so would replacing this control unit <https://www.skoda-parts.com/spare-part/3t0959121a-control-unit-skoda-41252.html> be the way to go?

The aforementioned microswitch clicked in mine but the black plastic spring tab seemed to be a bit farther than i like, is there an adjustment tolerance there to make before a replacement unit is made?