What is the issue?
PDF/UA > Metadata and Settings > Document Settings > Tab order entry in page with annotations > Tab order entry in page with annotations not set to S
What does it mean?
The setting, that the tab order should orientate on the logical structure is missing, for one page, for several pages or for the whole document.
How to fix it?
Go to the ribbon tab Extras in axesPDF and use the tool Set Tab Order.