iPlay 70mini Pro Display burn-in, display flickering, still no 90Hz

I have noticed that when displaying a static image, such as the system update screen, a kind of burn-in occurs. Another example: when I watch Netflix and it is not running in full-screen mode but in 16:9, black bars appear at the top and bottom of the screen. After about 20 minutes, the black bars are visible in the grey search field. This disappears again over time, but it doesn’t seem normal to me.

I noticed this for the first time after a system update. It took maybe 20 minutes, and after that the text from the update image was still visible in the grey search field, see pictures.

After 15 minutes of Call of Duty, the same thing happened, see pictures.
It is not immediately visible, but when you open the search field (the field in the top left of the settings), the ghost images are very clearly visible in the background.

Anyone can test this for themselves; the traces disappear over time or after a restart.

In addition, the display flickers (the image is distorted for a fraction of a second) sporadically. I feel that this occurs more frequently than before after the update to 4.0.25, especially when opening the app menu from bottom to top.

The display still does not reach 90Hz, tested on

https://www.testufo.com/

I have had four devices so far and all of them had exactly the same problems mentioned above.