Months ago with the help of my dad we properly grounded an outlet in the kitchen that had failed our initial home inspection. It took us months to get to the project because the junction box leading to the outlet was hidden behind drywall. I'm pretty sure that violates code everywhere, and even if it doesn't it's a huge PIA when someone down the line tries to make a change or in this case, fix what wasn't done properly in the first place. It literally took days of searching, moving the stove, drilling test holes just large enough to stick a tiny mirror in, etc. until we finally bit the bullet and cut a hole in wall of the hallway behind the kitchen wall where the outlet was located. Thankfully we found the hidden junction box, but unfortunately we were left with a big hole to repair.
While I had the joint compound out, I also patched up a few holes in our bedroom walls.