Pump Not Holding Flow During Priming

[smh]

The missus told me she shut the pump down because "it was making strange noises"

So I went out there and noticed the strange noise were a failure to have flow. The pump was making the high-pitched noise of a high rpm attempt to prime.

The bottom drain looked clean (no leaves). The pool skimmer looked clean. Pooled basket out and even the protective cover to the return. At the pump, its basket was clean. I opened the pump basket cover then retightened it. I inspected the O-ring later and it seemed OK.

When I turn the pump on, it starts a flow for the prime, air bubbles pushing out from the side wall, and there is a flow into the pool skimmer and into the pump volute.

It seems like it is going to complete its prime when the flow just stops. This flow stops at the pool skimmer and the pool volute. If there is an air leak, why would the flow be quite maximal during the prime and then just stop?

Not making sense. Is this solved by just replacing the pump basket cover O-ring, or is there something more?