Bug? Adding 16 note change rhythm

I’m adding a trombone part to learn fast working with Dorico.
I’ve add a half note, quarter note tied to dotted eight. I will ending with a sixteenth note. Dorico now change the quarter note tied to dotted eight into an double dotted quarter note. See images below. What is wrong?

Try going to Write > Notation Options, and changing the maximum number of dots you want to see in a simple time signature from 2 to 1.