Troubleshooting KV interface bug? Some buttons are not responding

[Yosh]

In the past months I've noticed that several buttons on my KV are unresponsive. Mainly the "downloaded" tab button on the main screen, the fonts button within a book and at the bottom of the screen, when the keyboard is visible, the 123/abc switch button.

I sometimes manage to click them if I swipe along their area, but most of the the time they are not responding to touch.

Since the "a" menu and the "downloaded" tab are positioned on the same location, I thought it might be a technical problem with the touch screen, but I have no problem selecting text in the same location, while reading a book.
So my guess is that there is some bug in the interface buttons.

Has anyone encountered a similar problem? Knows how to solve it?
My KV has the latest firmware, and looking back, the problem probably started with about 2 updates ago.