There is a purple crystal that the Kobolds are unable to collect in all of the Extraplanar Palace challenges. This is because it is partially embedded in a column that is part of the wall of the room. These Kobolds aren't equipped with picks, you know!
/loc results --- You are at: r1 lx2024 ly1064 i2051 cInside ox-180.05 oy42.03 oz-299.58 h261.6
Not gonna bother with screenshots because of uploading inconveniences .
I seem to recall there being a second one I spotted at some point, but I just did a very unthorough run through to check, and didn't notice any others. Now gonna send in an official bug report.