Can't close beam with dotted note

In the attached image I have a series of notes dotted eighth and sixteenth repeated twice. The score show a beam before the second dotted note. When the notes are added sequentially it is not possible to use beam properties to close the open beam section. However the second half of the measure shows the notes added as follows. Create the dotted note and sixteenth note then add two eighth notes. Join the beam covering all four notes. Then edit the third note to a dotted note and the beam remains. As an aside if you add four eigth notes and change the third to a dotted note, the beam opens up and won't close as long as the first two notes are eighth notes. If however the first note is dotted and then you close the beam before the third note and then change the third to a dotted the beam covers all four. So in this instance, the beam can't be closed with the first two notes undotted but will close in the manner describe.