PDF in EndNote turns white / blank

Some of my pdf documents attached to the references in EndNote turn blank and do not display any content longer. This seems to happen after annotating / highlighting text in the built in pdf-reader. The annotation/highlighting is still there, but no text or content in the pdf … see attachment.

WIndows8 (but the problem appeared also on my other laptop running W7), EndNote X7.1 (but I had the same issue earlier with an earlier version)

Any Idea what causes the problem or even a solution?

I am having the same issue using Windows 10 and Endnote 20.   I will follow for an answer.