Export to PDF/PPTX shows errors on some measures

I have a report with many measures on cards.

If I just open to view it - it is rather slow, but all measures show after about 10 seconds.

When I export to PDF, some of the measures show error (X) as if the pdf "didn't wait" for them to load.

PPTX is even worse - half of the measures are shown with X

Please help

Thanks