Axanar, I think you said you send feedback to amazon about your issues? That is the first thing to do. You obviously have some bugs there. I can't check the same books you did as I don't have access to the german store, even though I could read then as I am german. But I live in the US now.
I also use a Voyage now and I know my paperwhite 1st generation had a lot of issues. I had issues with reboots, lockups and all kinds of things. But I never used a PW2 or PW3 so I don't know if that was just my device or what.
I don't ever look inside my kindle folders, outside the documents folder. I don't really wanna know what is in there.
But I totally get being frustrated when stuff doesn't work. I gave away my PW as I couldn't take it anymore. I just thought I had a lemon or too many collections or too many books. No clue. Never had any of those issues with the Voyage. But I don't think that model is an option for you guys outside of the US.
I hope you can get it it at least to the point you can read on it.