Veigar's Cage didn't hold Shyvana
The link is to the replay of the game. The event happened at 19:38.
I got my cage up around Shyvana, she ulted out of it, being stunned as she left. This is the old behavior of the cage. She should have been stopped.
On closer review, it looks like she triggered her ult right as the cage went up on the far wall. She got the stun particles instantly, clearly indicating that the wall was up (the only other ally champion nearby was Vlad, who lacks a stun). Shyv's ult proceeded to go through the center of the cage, and through the opposite wall, standing stunned on the opposite side afterwards.
Pre-cage: https://i.imgur.com/9DTsv0v.png
Cage Up (note Shyv has stun particals): https://i.imgur.com/uxnC4P9.png
Dragon Form (still has stun particals): https://i.imgur.com/7a17NIx.png
Dragon Form mid cage: https://i.imgur.com/40rHdzL.png
Dragon Form far edge of cage: https://i.imgur.com/RpZtNxE.png
Dragon Form out of cage: https://i.imgur.com/Li7MV9g.png