I have the exact same issue. Could not find a solution. In my case, there are multiple subforms printed one below the other. If an expandable subform overflows into a new page, the last line overlaps with the text of next subform. I have added blank spaces between the subforms but, that does not solve the issue.
Finally, I have managed to minimize the occurrence of the issue by doing the following. Only turn on the flag "Allow Page breaks within content" for subforms that can really spread over many pages. All other subforms, turn the flag off. This minimizes the possibility of overlapping.