I think "bad play calling" is often confused with bad reads. The Sims fumble was clearly a bad read by Vad. DE was turned loose and went unblocked to Sims, though Sims should have still held on.
I don't know why PJ keeps playing Vad. Vad is a better quarterback but if we're gonna run the TO 75% of the time, play JT. Vad is not comfortable sticking the ball in the BB's belly and pulling it out when he makes the right read. We saw that with the play calling last week.