Question about tolino vision 4 HD

Hi digitec community Recently, a mishap happened to my girlfriend: she dropped her Tolino and the display broke on impact. Since I'm a passionate "hobbyist" and a new Tolino is relatively expensive at 140-170 CHF, I opened the thing up and then ordered a replacement display from a Chinese website (with the correct serial number of the original). I waited a few weeks, installed the new display and, lo and behold, the thing runs (almost) perfectly again. However, one problem has arisen and maybe someone has experience with it: The touchscreen of the Tolino only works when the backlight (reading light) of the display is switched off! That means: When the light is switched off, it works perfectly and without problems, but when the button for the reading light is pressed, it no longer recognises any touch inputs, or sometimes selects menu items without input (or at the wrong place on the display). When the backlight is switched off again with the button, it behaves normally again ;-P Well, maybe it's the replacement display, but I find it strange that the thing otherwise works perfectly. Does anyone know this "bug" or have any idea what the reason could be? My suspicion is that the calibration of the screen (with backlight) is set incorrectly. However, this is only a guess, I am by no means an expert.