Experiencing the same issue on Windows 10
It’s been happening for close to a month, and I know I’ve had at least a couple updates to Station, but here are my current details:
Station version 1.17.1
Most recent occurrence was tonight when I clicked on the Paper app, which I hadn’t used since I last “freshly opened” Station yesterday. As soon as I clicked Paper, a pop-up window appeared, which briefly showed a title of “collection-chooser” before changing the title to “Dropbox”. When I first saw this behavior I had both the Dropbox app and the Paper app, but I removed the Dropbox app, since I really only use Explorer to interact with Dropbox and I was hoping it would change this behavior, but the same behavior was exhibited. My current work around is to minimize the window for the collection chooser and ignore it.