We came across an issue with our group reports input control window.
This is causing customers with larger number of collections to not see them all AND unable to search for that collection.
The cause is currently unknown as engineering is working on a fix but we did find a work around that is a very minor inconvenience. Simply move the input control window any distance.
I wrote up a KB on it here: TEC1683608
I was going to create a video for the community but I had customer data loaded and didn't have the time to edit all those frames out
Here are the screenshots from the KB if you cannot view it for some reason (it was just written).