Doesn't remember where I ended

I am the very happy owner of a Pocketbook Inkpad (first version). Until now.
I installed a few dictionaries, tried to install for the first time text-to-speech and now all of a sudden he doesn't remember where I was with reading. Annoying.
When it starts, it starts with the home screen (although I tell him to start with the book where I left)

I tried the following:
- while connecting with my pc check the memory (no errors)

- format the memory by menu of the pocketbook (returns normal, still with the present date, but still starts with home, doesn't remember where I was, starts with the book I'm reading, but where I left before the installation of the mentioned files)

- a factory reset (got the double arrows and had to wait a little, but returns normal, still with present date, doesn't ask me anything, problems not solved)

I think the inkpad isn't able to write to files.
How can I solve this problem?:help: