I have not dug into this issue very deeply, a work around was quicker
.
But I thought I should drop you a note anyway.
On two occasions, after I had exported members "as CSV" the page controls (at least some of them, including the search button) had the function to repeat the export I just did. (Getting out of the page and back again resolved the situation).
It seemed like all that any button could do on that page, was to repeat the export i had just done.
Rgds , Ake2017