The use of slang in Tico Spanish is just as common as it is in any other language. Que chapa is one of those often used words in Tico slang. It would be helpful for you to understand why someone might call you a chapa.
Or maybe when someone is a collector of chapas? What if the old man lost his chapa and can’t find it?
Your move to Costa Rica obliges you to one thing: learn how to communicate with the locals in your community.
Que chapa can be translated into “what a clutz”. It’s someone who drops things, who falls all the time, who doesn’t watch out and makes mistakes for that reason. I was like that as a kid, I was a “chapa” most of my life. And I still am sometimes, because I always want to do everything at the same time and don’t concentrate.
In Spanish, being a chapa is being clumsy. If the damage is more serious, that person would become bungling, a dummy, a useless person, a fool, stupid or a moron.
In Spanish, in that same order, it would be more or less chapa, tonto, bruto, inútil, estúpido , imbécil.