There's a bug I've run into with Surface object when blitting as a backdrop.
The transparent area becomes an obstacle when the screen scrolls.
Here is a video demonstration of the problem, I have drawn a triangle to a Surface object, and blitted that as a backdrop to the frame.
Note in the video how I am able to collide with the backdrop no problem, but once the screen scrolls and I try to collide with it again, the entire box becomes a collision mask:
I have attached the MFA file of that demonstration to this forum post.
Here is the Gitlab source code of the Surface object: https://github.com/clickteam-plugin/Surface
I hope someone can help, I would honestly pay money to get this issue fixed if necessary.