Feeling a bit perplexed over this behaviour. I am prolonging the note with alt shift right arrow and get this result. Is that right, or is there a setting that I might have altered? The beaming and rythmic notation style is completely normal on other places. If I shorten the note with alt shift left and then lengthen it again with alt shift right it notates as it should.
I have the tendency of building on old files… All this is written in manually in Dorico from scratch, but the flow (or another flow in the file) might have xml origins.