The Android App has a very poor performance - especially when working with folders containing some pictures (50+). In most cases, previews are not rendered at all, and if they are it takes forever. The app freezes frequently to a complete stillstand, every once in a while to the point where the Android watchdogs querys if the user still wants to wait or if he wants to shut down the application (This should definitely not happen!).
When moving 25 Pictures from one encrypted folder to another it takes forever (>10 minutes) while there is a virtually no traffic. The target folder shows the files after several refreshes. This is also true for offline-files.
Most annoying: Boxcrypter is hogging excessively on the resources without telling the user (via notification for example) what it's doing and how far it has proceeded.
I'm using a Moto g(7) Plus with Android 9, and we're talking about pictures with an average size of less than 100KB(!); I'm using Boxcryptor with OneDrive and both apps (BC and OneDrive are set to ignore battery optimizations)