Polaris 380 Question

I have owned my house with a pool for 4 years and inherited an old worn out badly in need of repair Polaris 380. I have since restored the 380 back to its former glory by a rebuild kit 4 years ago and it up until recently has worked perfectly.

It seems that every year I have to replace some small part or another on my cleaner but this time I'm stumped. My problem is my 380 just does not have any "power" anymore. My pump is only a year old and (if the gauge is correct) has enough pressure to take the paint off a car (80 psi). So I believe I have tons of pressure, the tail whips around like mad and every orifice this thing has seems to spray water 50' in every direction. But when the wheels touch an obstacle in any way it just stops. I can touch it with my finger and all 3 wheels stop. It moves around the pool but not with near the vigor it once had and not my pool is looking kind of dirty.

I've taken it apart and replaced the seal at the bottom of the connected fitting (o-ring seal).

Where do I look next? What are your thoughts. Thanks in advance for all your help.