If the problem is due to my poor worksmanship and it has always been there since the very beginning (even though you may not have noticed it for 2 years), I'd g

If the problem is due to my poor worksmanship and it has always been there since the very beginning (even though you may not have noticed it for 2 years), I'd gladly fix it for free. Of course, with a bathroom door you'd have to prove it's not due to wear and tear, but this doesn't apply to software - the bits in your binary don't change with time.