I’ve never dried anything that long indoors, but from what people told me when I was researching the best way to dry some red oak I had milled there are issues drying indoors doors. Wind does most of the drying outside.
Did you use a moisture meter?
Worse, I've been told that attempting to dry indoors would result in rot (given not enough air flow, which might not be the case in all indoor environments), and consequently have never tried it. I've exclusively air dried pine, oak, poplar, pecan, cedar, all under open walled structures and not had too many problems over the last 20 years (and my dad was doing it for another 30 before that).