I have a version of M9 where everything works exactly as expected. It is using jdk 1.8.0_65. I have installed version M15 on 3 different computers using jdk-15 and get the same results on all 3.
When I right-click on an ou and export to either excel or csv, I only get a single page of results. The default is 100. I get this to return more by changing the paging size, but it will never return more than 1000 records. I have experimented with all possible combinations of paging settings.