I had a inflator that was slowly leaking from the bladder thru the inflator. It wasn't much of a issue when I was neutrally buoyant underwater, but when I am on the surface and inflated my bladder, I can feel hear the whizzing from the inflator.
It had a what looks like a soft sealed inflator button that is held in place by a screwed down flange, which when I tried to open up, the whole disintegrated and there was no holding back the air from the bladder. I was on a liveaboard and we changed the stem and it was still leaking. I asked the captain for duct tape to simulate a sealed button, but he told me this is my life I'm dealing with (he's saying its my life after he tried to use a plastic sheet as a substitute for the button) so I agreed to rent their crap for the whole week. I probably could have used silicone tape and fixed that thing there.
Never seen that type of inflator. Either it is ancient design or there is some mysterious leak in the inflator's body.