Skimmer sucking air into system

Good afternoon
We installed a new pump 8 weeks ago. All good.
Today our skimmer is sucking intermittently as if it’s taking in air.
My husband has checked the pool water level, let a lot of air out of the sand filter, baskets clean and no obvious pipe problems. Everytime he primes the pump it sucks air again.
I suggested perhaps a new joint was the problem which he took very personally.
Next week we have visitors and I was going to shock the pool anyway as we have a touch of algae.
We rally are panicking now.
Any advice very welcome.

We have checked skimmer plate and was a bit stiff.
Hopefully it’s just this, phew!

Keep an eye out for anyone in the pool playing with tennis balls or anything small enough to pass through the skimmer’s and jam the weir gates open or shut as either will affect water flow into the pump.


Often had to take a bit of sandpaper to the weir as they just catch


Where do you sand it?

Around the perimeter, anywhere where it may get stuck.