Why do my airpods pro hang up when I remove only one of them? and how do I change that?

Recently, when I remove the right airpod pro from my ear, it hangs up the call I'm on (I start the call with both airpods pro in). This didn't happen until a few weeks ago. I want to be able to take it out and stay on the call with the left one in, but it doesn't work and I can't seem to find a setting for this that I might change.

Does anyone know what's going on or how I can change this behavior back? Thank you!!