Oh man, that stinks. I've done the exact same thing with my slow cooker for years, always filling it to the top because I thought more food meant more flavor. It took me making a really soupy, bland chili to realize the liquid wasn't bubbling right and everything came out watery. You're not alone in that, it's such a sneaky mistake.
And it's funny how that goes with so many things in life. We think more is always better, but sometimes it's actually the limits that make stuff work right.