Yeah, I can think of three possibilities off the top of my head. While spooling mode is a possibility, I wouldn't expect it to come to a complete stop.
1. Sticky shed - as Sweetbeats says, what kind of tape is it?
2. Tension too low - where the tension is servo-controlled, there's usually independent settings for play and fast wind modes.
3. Brakes partially on. On my B77 this happened, it would slow to a stop when the braking force equalled the tape tension. However, that tends to be on machines with static tension, and I believe the MS16 is servo-controlled.