You are not accurate enough. Which OS is on unit exactly? Android?
(There are only two possibilities - WinCE or android)
Permission may affect the operation, but TTS folder only serves ony for reading, no writing, so this is not culprit.

I guess Win10 made a problem. It often writes to USB/SD hidden (volume) folders and is able to make some changes in system structure.

Btw, this "problem" of yours is no place in this topic. Will move it later.