It's probably doze mode from Android 6.0. If it thinks you aren't using your phone it'll shut down unimportant tasks like PitDroid. I've got a fix for that in the beta version if you want to give that a try. Hope your meat turned out ok.
Downloaded the app....did a lot of reading here and searching google, but if i try to change the pit temp. it says authentication failed. I saw some answers here, but it's a lot of abracadabra for me (sorry). I have the HM working (wifi and ext.) on my laptop (Windows). Dit setup a password there, but Pitdroid still says authentication failed. Does anybody know what i have to do to make this work? Sorry if i am interfering, but i thought this would be the suitable place to ask...