I have a multi-page exam where the markings for a particular page are never read and require Manual capture. It does not matter how dark the used pen is and what proportion it covers, it still does not recognize it. Also a reductoin in the B&W conversion threshold and an increas in the default darkness threshold does not appear to improve the situation. Marks on other pages are read correctly despite them often being fainter. So it must be strictly related to the page/question. I also recompiled the document and re-detected and re-checked the layout without any improvement.

Also, when I hit zooms on the page in question I get neither unchecked nor checked boxes. The layout page recognizes the corner marks and the page ID but has no boxes around the place where the answers should be.
However, under the Preparation tab, I do see red boxes in the places where they should be when I request to 'Check Layout'

What is going on?

Stefan