Triplet Copying Bug

Hi, see attached. r 1390, windows.
I was trying to copy measure 9 (the one with triplet with the stems up) to measure 29 (the one with the rest). Did this numerous times and every time the system crashed.
I had just copied the other measures with triplets and they worked fine, so the only thing that looked different was the stems pointing up. So clicked on the "A" (first) note of the triplet and "x" to flip stem directions (to down) and copy now works fine.
I can do this time and time again - flip the stems and "UP" crashes and "DOWN" copies OK.
Thanks
Dave