I had started the app for the first time. I had added an MKV file by drag-and-drop. Then I want looking at the settings (I changed nothing)
I went into the Advanced settings - changed nothing.
Error occurred when I exited the advanced settings.
Note, that the "Send Bug Report" feature of the app doesn't work very well and you don't include your email address anywhere. Consequently I came here and setup an account so I could tell you about the problem. Thanks for your hard work.