How to fix error message "com.android.cts.ctsshim has stopped"?

[AC Question]

I've recently updated my galaxy s6 edge to android 7.0. Ever since then, I can't access my messages app (the system app not whatsapp). This error message pops up: "com.android.cts.ctsshim has stopped" or "com.android.cts.ctsshim keeps stopping". Any ideas how to fix this? I'd rather do a factory reset as a last resort but all advice is welcome.