The SCPH-5501 models have this problem, that is why they redone the PlayStation three different times. The later PlayStation models doesn’t have this problem. You can find a later model on Ebay or Amazon for a reasonable price.
The Dualshock 3 (PlayStation 3) controllers from Sony don’t usually last long. They are made cheaply and wares out real easily. The 3rd party controllers honestly works more better than Sony’s controller does.
It sounds like you wore out your controller. You could repair it or just get another controller. I wouldn’t mess with it, I would get another controller.
You honestly might want to just get another PlayStation 4 controller. Using the one with the water in it can catch on fire or stop in the middle of a game you are playing.