I have a double master bathroom vanity with 2 2 sinks. On one side, the hot water valve closes by itself, it's a push/pull plastic unit, and the other sink is fine. What causes the hot water valve to close (push out) the valve button constantly. I have to push the valve button back in for the hot water to work and it sill stay for a while, then eventually pop out to the off position. Please advise.

We need the brand name of the valve. How old is it? If you don' have a model number a picture would be nice. Back to you. Tom