Sounds like it's time for a new top. Please call Heartland Customer Service at 877-262-8032. They are real easy to change out. I had to change mine as one of the glass shades from a ceiling light came off and fell onto the top. Oops!
My friend Terry H used some fishing line to cut the silicone seal around the top, we unplugged it and pressed up on it from below and it came right out. Cleaned up the silicone from the counter, added a new bead, put the new top in, placed something heavy on it for the day, plugged it in and viola!