Spinning wheel - app not responding

The last two days I have experienced problems with DevonThink 3. The app stalls all the time and I cannot open the database with all my research (it opens and then the wheel just keeps spinning). When I open it, I am notified that the database seems to be already in use, which it is not. I have tried to reinstall the app and download the remote database to start over. It took two-three hours and it made it work yesterday, but this morning I see a spinning wheel once again and cannot do anything with the app.
Did anyone experience something similar? Which steps can I take to avoid this? The issue makes me worry that I cannot rely on this software for my research and work. With all files locked in a database that will not open, I have no idea what I would do if it occurs before teaching or a presentation.

Could you please launch Appleā€™s Activity Monitor application (see Applications > Utilities), select the frozen DEVONthink 3 in the list of processes, choose the menu item View > Sample Process and send the result to cgrunenberg - at - devon-technologies.com? Thanks in advance!