FLStudio stopped working" appeared. So I had to manually crash FL by left clicking. Black screen appeared when FL got closed, since OBS had to register the full window of FL.
Hope this better helps (it works on any pattern ...
Fl 11 and 12 and 20 are registered however my vst's are still in demo mode i think i may have dragged another fl file containing the same vsts that fl comes with in the library and somehow rewritten ...