I noticed that when inputting chords that you plan to then change the even durations to dotted followed by shorter, (using the period shortcut key), that it is important to first turn off chord input (Q) before hitting the period key shortcut, otherwise unexpected results happen. I show this in the gif below - first with Q mode selected, then I undo, then repeat the process without Q mode selected. I thought this may be helpful to someone out there.
And now I realize why this is so. It is because some modes are cumulative and by invoking the period ( with Q enabled ), I am asking the program to change all selected notes to dotted notes, hence the ties.