New Washers in Shower Faucets

Recently, I had a plumber replace washers on a 35 year old Phlyrich shower faucets which had driped. The plumber said they were Price Phister type faucets. It does not drip any longer, but after turning on either hot or cold, a minute or two into the shower the stream just stops and one has to continue turning on the faucet to get the water to come back on. Why is this happening and what is the is the solution?

shower

Remove the shower head and see if it happens.......

I will take the shower head off and try it. It's an older model Speakman with no flow restrictor.

faucet

The washer has probably came loose and needs to be reattched. I am not sure if Philrich used the PricePfister system the way several other companies did, but if so, there might have been a better repair than new washers, depending on which trim pieces you have.

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I think the design was called Philrich Imperial. The plumber was the one who thought it was Price Pfhister innards. If you turn the handle back and forth when the water stops flowing you get a thumping sound....like something is slipping back and forth. Maybe it's time to call the plumber back in????