Issues after marshmallow update and phone format

A

AC Question

I have a Samsung Galaxy Note 5. Updated my software to marshmallow and everything went nuts. Data won't stay connected, wifi drops, email wont sync, apps crash and dropped calls or just going right to voice-mail.
Cleared my partition data and did a full factory reset and the problems just got worse.
Any ideas what I can do to fix this thing short of getting a new phone.