PDF page goes blank when editing

We are using Acrobat 11 Pro and some users (not all) when editing (adding text) to a PDF page, while they are typing the page just goes blank and clears all content on the page.

I have watched them do this and not sure what is going on, but apparently it happens to certain users and not all. They basically will click add text, type, and then the page goes blank. This happens randomly and not all of the time, but often enough that it has become a minor issue.

Has anyone ever encountered this or would know of a solution?

Thanks