I tested latest Pinta 2.1-dev on Ubuntu 22.10 and I see this dashing problem fixed.
Just a little note. What I see now is when rectangle is drawn, mouse released and moved away from object, and move mouse back to rectangle edge and now arrow icon appears. Before this merge it was hand icon. Actually I like this tip arrow point mouse icon more, because it more precisely determinants where exactly rectangle is going to be curved (at tip point of point arrow).
I tested latest Pinta 2.1-dev on Ubuntu 22.10 and I see this dashing problem fixed.
Just a little note. What I see now is when rectangle is drawn, mouse released and moved away from object, and move mouse back to rectangle edge and now arrow icon appears. Before this merge it was hand icon. Actually I like this tip arrow point mouse icon more, because it more precisely determinants where exactly rectangle is going to be curved (at tip point of point arrow).