Custom Move/Resize doesn't stick

Greetings - I've written an action that runs a custom move/resize on Safari, but when I drag the window by the toolbar, the window snaps back to its original size. It doesn't matter if I switch windows between the resize action and the drag.

Is this a known issue?

Thank you --

BTT 3.626 on macOS 12.0.1, Safari 15.1, MBA M1 2020