I have the odd problem (touch wood), but then every shop owner who runs a bricks and mortar shop has theft and really daft/awkward customers to deal with.
That's life, you deal with the public, and you get all sorts.
Apart from thieves, I have found that all a customer really wants is to be treated with respect, and have their needs or complaints heard..
I know there is always an exception to the rule but generally speaking, I have never seen a vegetarian Shark (whatever that means).