Problem with toilet install

I am installing a new Kohler toilet. One of the hold down bolts on the old toilet was so rusted i had to hacksaw it off. Then when i pulled the toilet off i had alot of difficulty removing the remains of that bolt from the flange. The other bolt installed fine and held in place firmly the one i had trouble removing would not lock in and stay for proper installation . Any ideas on what i could do? I don't believe i did anything wrong in removing the old toilet but let me know if you think i did.

This is interesting because i have Briggs toilet in the guest bathroom that works fine but has a hold down bolt that won't stay in place causing that side of the toilet to tip up if weight is on the other side. That will be my next project.

There are replacement or repair flanges you can use.

A picture posted of the closet flange needing repair will surely yield repair suggestions.

I will try to post a pic. Not sure what good it will do. It would just show the black plastic flange no cracks breaks or problems you can see.

Sounds like you may have just run across where the toilet was installed using zinc plated steel closet bolts... The good choice is 5/16" brass closet bolts.