I added another Xenon to my mesh of three, previously I have always used the Argon as the assist node but this time I used a Xenon. Mesh network was all working correctly at the time. All seemed OK until it asked for the mesh password which it then repeatedly said was incorrect. I tried many times after reboots, restarting the app etc but no dice. The first password I used could have been wrong. Eventually I went back to using the Argon as the assist device and it worked straight away.
Still seems to be happening in 1.4.4 for me. For anyone else facing it that doesn’t have a non-Xenon, you can use my patch in Xenon stuck listening (flashing blue) to allow a new node to be added with any password. Just remember to undo the patch after you add what you need.