Don't worry, you can loot crown crates instead.

There is a way to loot it but you must be so specificly placed it s just anoying. Like how they ignore the fact dks leap also sometimes is out of range unconditionally

I've reported several treasure chests that appear underground, eg. treasure chest near the blacksmith survey report site on Eastmarch, that you only know they're there because the keen eye visual effect.
Nothing has been done so far to fix their positioning.