We doublechecked and did some additional testing and were not able to reproduce the issue with R81 or R81.10. We need you assistance with more information to pinpoint the issue and understand the specific conditions in which this isn't working.
First, it would help if you install the latest recommended JHF on the Management server (and log server if they are separate). That way we won't troubleshoot old issues that might have been resolved.
If you still have the issue (on R81 / R81.10) and cannot export more than 10K logs, please open a TAC ticket. They will work with you to gather the information and we will be able to further the investigation.
Once we have a solution, I'll also update back here on the post.