Yep, it's a broken stab wing tube. About the only way you can do that is by levering the stab up and down while trying to put it on or take it off. The tube to tube fit was probably too tight, and rather than enlarge one or reduce the other, they tried to force it.

Next time, either enlarge the opening inside the stab a little, or use some 400 or 600 grit wet and dry sandpaper and carefully sand the aluminum tube by rotating the tube while you sand it. You want a snug fit. Not loose, not tight.

SkyDude, that was as good as it gets.