Have you had the transmission fluid level checked, this is one of the most common causes of a trans slipping and with these sealed trans no one ever has the fluid level checked??
Yes did the drain/refill with a new filter. Odd thing... replaced a cracked vacuum hose and cleaned the throttle body (it was bad) and the problem has subsided a lot. Kind of crazy, but I think the trans wasn’t sure what to do at stops as it was still swing some throttle. I actually did manage to find another post of someone experiencing a similar problem (with a similar solution).