I notice lots of people have problems with “Empty Trash” so here’s another: when I click “Empty Trash”, the emails do not disappear immediately from the trash folder. I have to go to a different folder, then back to the trash folder before they disappear. This is not a big deal. Just thought you should know.
There were some issues with version 8, while in beta, where folders would not refresh. I am not seeing that issue in the latest release, but it could be related.
All I can suggest is that you download and install the latest version from the Release History.