After merging 2 documents together, the parent tree entries for the second page do not match their expected key. For the attached document you can look at the "Date you are available" field after the merge. In the parent tree the second page field is located with key of 15. However the object expects its key to be 21. The /StructParent value is 21 but it should be 15. This mismatch causes issues with a11y readers and the reading order in Adobe DC.
The fields brought from the destination document are correct, but fields from the source document do not match. They continue with the pattern, so the next field is located at key 16 but the /StructParent value is 22, 17 for 23, etc.