It's odd.
A) With the load balancing on, side chaining the 3rd party plugins will crash Sonar when trying to start playing.
B) With the load balancing off, side chaining the 3rd party plugins will lit both the play and pause buttons yet it won't play and won't crash Sonar (you have to end it manually).
C) Side chained, Cakewalk MB will play yet it won't use the side chain input (like it were silent).
D) When inserted a plain buss-to-buss send, it halted and crashed Sonar like in A).
Whoa?!