I have a scene that in 1.4 would show lots of balls bouncing across the scene. Basically I made multiple copies of a ball, setting the X,Y starting position to something different for each one. I set the gravity to point slightly sideways. So as soon as the scene starts all the balls start falling and bouncing across the scene. (No triggers are used.)
In v1.5, it looks different. Only one bouncing ball I can see, and other balls seem stuck to his hair!?!
Settings in case useful.
Problem solved. I zoomed out in the scene window and saw what was going wrong. In v1.5 the balls are bouncing off the rear of the puppet (Sam). One started on top of his head and got stuck there. So the question should now be "why were collisions not happening in 1.1". But I don't care. In the scene I changed the Physical/Collision/Start property to "When triggered" for Sam (which effectively turned off collisions for that scene only - I don't have any triggers in the scene) and everything started working again.