Replacing Glass, problems with the screen

Hello guys.

Recently i replaced a lot of digitizers that are glued together with lcd's (for example in samsung, apple etc.).

But there are some phones that there are no molds and you cannot glue them together with LOCA.

Is there any way to get rid of such "stains" as on the image below?

Maybe there is some protective film that you can put between lcd and digitizer?

This stain occurs when you apply a little force and the digitizer is touch the lcd.

Any help would be appreciated