I rarely use the baster in my kitchen (I have about a half dozen I use for my garden things! lol), but I know what you mean, about it not holding the liquid - the seal isn't always great, though sometimes they are pretty good. And when you turn it upside down, with hot liquid in it, the air inside can heat up and expand, shooting the liquid out, as you described.
The baster in my kitchen is a very old stainless steel one - the only one back then, and the rubber bulb has decayed several times. I just buy a dollar store baster, that looks the same size, and the bulb lasts another several years.
I have one large baster, I use for garden purposes, and the bulb didn't seal very well, so I just used duct tape! Doesn't leak a drop now!