http://en.lichess.org/study/ZM1r75zqWe can not move pieces in the way that checks are ignored. So I believe we need to remove checks for antichess studies.
Switch from Standard position to Antichess :)
Well it was antichess. The incident happened in Chapter 1
I maybe found it... It is the owner of the study that can't do it... I created one and there I couldn't, but my friend could.
hum.. I tried it myself at this particular game (cat_person board) and all I was able to do, was to move the King out of the check and /or (in terms of Anti|Chess) had to bypass that specific setting.
its private Zeta.. can't access it. maybe u pm this one.
I think this bug has been fixed.