Long story short - Bought a TM-AC1900, successfully converted it to an AC68U, had AImesh working with multiple nodes, etc. I eventually replaced my gear and this has been on the shelf unused for a year. I would like to reset it back to a T-Mobile device so I can give it to my mother to use a Fem2Cell as originally designed. I can't find any guides on how to go BACK to a TM-AC1900, any advice?