Nothing collides unless you explain to the game that you want it to collide.
Maybe you have given them certain behavior or made events for them to collide.
A simple solution is to disable their collisions then they will not collide with anything.
Otherwise you don't have to have things solid to collide. You can easily have them not solid and just for the player or enemies create an event of collision with them.
Basically you have some configuration logic error.