[McAroni]

Javier MM could you try the following: in the file where the text shifts to the side while editing bring up the overlay and tap the 4th icon on the bottom. (scale mode) cycle through all the scale modes (fit to page, half page, ect...) go back to your preferred scale mode and try editing the text again. I saw the shift on my Samsung and after I have done this the inserting and editing of the text was fine. Maybe this helps. 

Thank you for your help. I have tried various scaling modes and the text still moves around when I edit. 

I found another file where the text input was off.... Try again the cycling through the scale modes, and after that reset the crop of the file. Then everything was fine again.