Mobile user's pdf are just static

We had a user recently send in a ticket that when he opens pdf on his phone, they sometimes show up as 'tv static'. I've had this issue in the past with another company but it was on desktop and it turned out grayscale needed to be turned on. This issue persist on all copiers, his phone is up to date and so is his apps. If anyone has any clue what's happening here, any steps would be appreciatated, cannot find anythign online that's related. I attached a picture to show you exactly what I mean.