Form Checkboxes - Sometimes work correctly, sometimes not

I am creating a fillable PDF form for the first time. 

I have an issue with the checkboxes and radio buttons. 

Sometimes they work correctly and sometimes they don't on the same form. 

I open it one time and it works. I open it another time and it doesn't work. 

It should only allow selecting either Pass/Fail or Yes/No, not both. 

When it is not working correctly:

If you click Yes, and then No, the Yes is still filled, but not completely while the No is filled completely. 

If you click Yes again, the Yes is cleared, but No is only partially filled. 

Clicking No again clears the No checkbox. Clicking No another time results in the check box being completely filled while Yes is blank, as it should be.