Using the Android app, I cannot enter an advanced repeat "Every Weekday" or "Every Mon, Tue, Wed, Thu, Fri". The app reports an error "Invalid Repeat".
I can only add "Every Weekday" to the task if I use the PC browser app.
If I do that and then go back to the Android app, synchronize, and open that task's advanced repeat, the Android app shows the advanced repeat correctly as "Every Mon, Tue, Wed, Thu, Fri". But if I simply touch "OK" without making a change, it again reports an error "Invalid Repeat".