All of these examples are the exceptions, I had one myself who complained after I cleaned a cat urine saturated carpet that stank to the heavens.The whole house which was huge stank from top to bottom of cats mess, not nice if your allergic to cats like me

I explained there was no guarantees and she agreed, I cleaned and the stains as predicted did not come out but the smell went.
She duly paid up but 3 days later rang to say I has made the stains worse than before :

but the smell had not returned.
She wanted me to call and clean again (normally not a problem but I knew it wouldn't end there) if not contribute to a replacement carpet

I told her there was no chance of that, I did not want her as a client as gave her a full refund with out prejudice. End of
I don't want this type of business she was trouble and a conwomen and I would rather get shot of her asap and move on.
Think about all the clients that love you

not the ones that try it on and do there best to ruin your day,week,month what ever these clients are 99.9% of your business so why worry.