Beam corners can occur when a change of stem direction within a beam is combined with a break in the secondary beam group. This can be at the end of a subdivision or at a change in rhythmic speed.
Beam corners do not follow accepted rules regarding the order and rhythmic meaning of secondary beams, and can be confusing for the reader.
Dorico Pro avoids beam corners by analyzing the pitches and stems within a phrase, and implementing stem directions that avoid a beam corner.