Hello, I'm testing the solid behavior too and i have the same problem.
Adding the solid behavior to an object is not enought to make 2 solid objects "collide" (don't pass through) ?
Isn't it the solid behavior task to prevent solids objects to pass through other solids objects ?
I see that if i add physics behavior on the objects, it works but it's not the solution, i have walls that falls to a side if i add physics on them..
How to prevent 2 solids objects to pass them through ?