screen failure after battery replacement

Dear dudes

my old ipad pro 12,9 (2nd gen) needed a battery replacement. Unfortunately Apple does not provide support for such a replacement and i needed to take my ipad to a non-authorised lab which usually make this kind stuff. Unfortunately now the screen has problems (see the shaded wobbles around the edges of the screen in the picture). The lab guy is saying that it's their fault and they are looking for a new LCD screen to replace the old one. However i'm not completely sure the LCD failed but maybe it's the pressure from behind which is not uniformly distributed. What do you think? I'm a bit worried of replacing the original LCD screen with a (probably) third party one...

Please any advice?

Regards

Alessandro