@doniks it always happens. Never got to make this work with my email provider; however, talking to other Dekko users it could be due the email provider itself that I use (outlook/hotmail), since other people don't experience the same issue with different providers...I remember the original Dekko's creator tried to help me to resolve this issue, but never accomplished since also to him seemed a weir behaviour.
EDIT: to answer your exact questions. It happens always when I try to reply to an email with both reply options; I guess it happens with all kind of emails, but I made only random attempts to see the effect and the app allways suddenly crashed. For the log, I didn't check, I will try to see later if I find something useful.