Fourth ritual alter not clickable/starting

Hello,

"Occult Devotion" is allocated so that I'll always get four ritual alters. Sometimes the fourth alter is not clickable - I tried leaving and reentering the area, nothing works. There are no more monsters around the alter and the minimap shows it to be untouched.

https://www.pathofexile.com/forum/view-thread/3728884.

Another report, however the op there is unable to do proper research for previous bug entries.