I guess that was problem. Strange. It’s set to collision per default on Sprites. Might have to change default values on Flipbooks to be First Frame Collision as well?
default is set to No Collision because it’s less expensive to use a standard collision box component in a Blueprint instead of using Flipbook collision, and it’s generally better practice for performance not to use it if it’s not necessary.
For reference, first Frame Collision will use collision from first frame of flipbook, and Each Frame Collision will update collision to match each Sprite used in Flipbook. latter is obviously expensive as it recreates physics state every frame.
If you enable Collision Source in your Flipbook, it does use collision from your Sprite. Depending on setting, it will use collision from first Sprite in your Flipbook, or it will update to match collision from each Sprite in Flipbook.