94 corolla can't shift out of park

My 94 AT corolla has touble shifting out of park. The button can't be pushed in hard enough by hand. I have temporarily remedied the problem using a C-clamp which gives enough pressure on the button to "unlock" the shifting lever. What could be causing this?

I have 120+ miles. I do push down the brake while attempting to shift out of park. The car runs fine, considering the 120+ miles.

Thanks