I'm only at the druid grove but did come by the harper's stone and I also had problems moving it. Only since patch 6. I could move it, but only in tiny steps. Shadowheaert pushed it away in 3 times, every push moved it just a few "inches" sideways. Finally the chest became accessible.
If you pointed a little too far, you got the no space or too far message. (Or maybe some other like can't reach) but if you then pointed a little closer it became ok.
