Losing place in reading list when phone reboots

What exactly is lost - the current sentence in the current article (e.g. it returns to the start of article), or maybe it even loses the track of what was the last read article?
Also, is the app speaking aloud when your reboot and the problem happens, or is it paused? The more details I have to reproduce the problem, the better.
 
Will try to reboot my phones a few times like this to see if I can reproduce the problem, thanks!

Do you run any kind of system "cleaner" app, like Power Clean, Clean Master or similar? They tend to delete files in our data folders, which could cause such loss of data. Please tell me if you do use any such cleaner, and which exactly. Usually you can enter "exceptions" into such apps to leave certain files or folders intact. If you can, enter there the entire @Voice data folder and mark to preserve all content in its sub-folders as well.

Just noticed an oddity. After a reboot when reading progress was lost, exiting the app through the exit menu item, then restarting it seems to partially restore the progress. It opens the text file that was being read, and resumes reading at a place before the exact place I left off.

Additional questions: Where is your @Voice data folder located - on the main phone memory, or on an external SD card? What kind of SD card, is it large, fast or something relatively slow? I'm trying to understand all the issues, maybe there is something like a timing issue, where it reads data too slowly... Even looked at used Doogee X5 phones on eBay, $65... but could be that I spend the money and still won't be able to reproduce and understand the issue... Is there anything else you can think of to help me reproduce this issue?