This message is due to the :Top12 minicalendar modifier being incompatible with the current 5-weeks minicalendar option.

These settings are mutually exclusive (cannot be used at the same time), as the :Top12 modifier is already a way of dealing with the case of months that cover 6 weeks (by handling days 1 and 2, instead of days 30 and 31).

Topic 177325, last updated on 19-Apr-2020