prodigy p3

Since you bought your Rookwood have you removed each brake drum and inspected the brakes and bearings? Greasing or packing the bearings is a must since it is a 5 year old trailer unless you know they were packed just before you got it. You can either have all of this done or do it yourself. If you choose to do it yourself then you can Google "Packing RV trailer bearings" and "Adjusting RV trailer brakes" if you haven't done that before. I do all that kind of work myself because I trust me.

I have the Tekonsha P3 and am very pleased with it. Maybe one reason it doesn't slide the tires is because your newest trailer is a heavier trailer than your last one. I make it a point not to slide my trailer tires. You want enough braking on your trailer to be balanced with your tow vehicle for good controlled stops.

Edit: One more thing I thought of is to check the electric braking action. With the wheel jacked up and the trailer cable connected to the TV, spin the wheel to check for easy turning. Now have someone press the brake pedel while you check to see that the wheel is locked.
Do this check for all 4 wheels. Keep safety upper most in your mind while doing this.