Hey Samuel,
I think I managed to get one step closer to a possible way of fixing it. I used my multimeter to check if there is continuity for all the pins and I found out that in my case two pins have no connection although they should have. Those are 2 pins that switch the layer in this multilayer-cable, so my assumption is that it is a loose connection between 2 layers. I tried pressing them back together using a small vice, which didn’t work. Now my plan is to ask a colleague who is good at soldering to bridge those pins using extra wire… If this will not work, my last idea it to use a FPC to breadboard adapter and make a new cable myself.
This really is a shame… I contacted gearbest and alldocubes official store on Aliexpress and neither of them could help. I cannot understand how can produce a tablet and not have the parts ready… So I think the only way to fix this problem is diy, which really is a shame. I am pretty sure this will be my last cube tablet…