I have a horribly low acceptance rate (<20%) and am curious to know if I'm the only one and what to do to improve my ability to test edge cases.

The issue is that I tend to submit as soon as I pass simple test cases, and then I get an error or a wrong answer for more complex cases. I'm usually able to fix these since my algorithm is usually correct, but it's discouraging that my acceptance is very low (when I see some others with 50-60%) and I'm wondering if companies will penalize me for missing certain edge cases in an interview. Anybody else in the same boat?

I mostly on do Medium difficulty problems.