MS gets confused when changing note length

In attached score there is a problem when I try to change the length of a note. In an earlier session I copied/pasted/removed some weird measures (resulting from midi input). Now, when I try to change a note from 1/4 to 3/8, some of these measures appear again in strange places.
When I then undo, and lower the note by a half tone using the arrow-down key, and then again try to lengthen it, all goes well.

I made a movie of this, but it is too large to upload. I hope my description is sufficient to reproduce the problem. (For me it is reproducible, also after saving and reloading the score.) The note in question is the A quarter note on the lower piano staff in measure 24, second beat. I change the length by pressing the "." on the toolbar.

Score attached.