I just upgraded my Fairphone 2 to Android 6. Messages is now behaving strangely.
I have 3 messaging apps - Messages, Signal and Mighty Text. Messages is set as default, but it appear to think that Mighty Text is the default. Messages will receive messages, but when I try to send, I get a message that says “To send, set Messages as the default SMS app” with a button “Change”. When I tap Change the message disappears.
I check my settings and Mesages is listed as Default. I have tried changing defaults to and fro. I have tried deleting Mighty Text. No joy.
I am now using Signal to send messages, but Mighty Text (which I use regularly on my laptop) does not see the messages I send from Signal, though it does still see all incoming messages, whether they go to Messages or Signal.