Maybe you're right, some pdf files are now in preview mode, but there are some strange things happening.
Well, we'll see.
I've stored the image file on a second HDD as it was too large (170 GByte) for my C, but the second HDD is a simple old mechanic 2.5 inch 5400 one.
I'll replace it with an SSD, maybe there's a speed problem causing those strange things.
I'll come back to the topic.