Wasn't tested very much in vp9 was it?

No matter, it's easy to fix.
For
VP9, disable collidable on all the walls for the shooter gun. Then it's ok again.
S1 through S32, Wall4, and Wall5.
You can do this in a snap by using a group select box around the square and kicker, pressing shift and clicking on the apron wall, then right click on the apron wall and choose draw in front.
Then group select all the walls, hold down shift, click on the kicker and square wall, uncheck the 'collidable' box in the properties.
Then click the apron wall (wall4) and uncheck the collideable box.
All done.