How easy is it to damage the burrs?

I was trying to find true zero and something strange happened. I was at a certain point where the burrs weren't quite touching, so I went coarser briefly and then went back in the finer direction, however it seemed like the point that was fine before suddenly was scraping and quite loudly. It's not like I went way past or anything, but I did accidentally get more than just chirping, to a more constant contact sound for about 3 seconds.

After this it still seems to be grinding ok by the looks of it, but how do I know if I've messed up the grinder?