EndNote created about 3000 empty group sets for unknown reason, how to delete them quickly?

EndNote EndNote General
1

I don’t know what happeded, EndNote created about 3000 empty group sets with the same name just after I created that group set. How can I delete all these empty group sets quickly (not manually delete them one by one …)? 

Thanks.

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2

I am currently using EndNote X8, but this problem appeared when I was still using X7.

3

Call tech support!  www.endnote.com/support