Bug Can't change slider with game controller

Trying to make menus with only the UI Toolkit.

I drag a slider on and do nothing but style it a little. When I launch the game and open the UI, I can move around the UI and get the focus to the slider using the controller, but then left/right on the D-Pad won't actually move the slider value up and down (nor any buttons on the controller). The arrow keys on the keyboard move it but the controller won't, even though controller functions work otherwise.

Anybody seen this?

PS5 DualSense controller.