water overflows from skimmer when I shut down the pump

I own the in ground pool for more than 10 years, just replaced the pump and motor during the winter, it works fine until about few weeks ago, I noticed everytime when the pump shuts down, the water will overflow from skimmer, the overflow is very strong, it knocked the basket off and water reaches all the way to ground (that is about 6 inch higher than water surface).
Any idea what cause this?

Thanks!

Maybe air in your filter? Is there a bleed valve on the top?