I managed to reproduce it and uploaded a video (beware, the video upload is from some random file sharing website):
Hmm, that isn't intentional. I think I know what's causing it: slowing the game's time down means I also have to reduce the time between each physics update, otherwise everything would look choppy. The increase in physics updates coupled with the slower player movement speed means the game manages to register the collision between the barrel and the player, hence the player being stopped. I can probably just reduce the radius of the barrel collider and call it a day.