Hi! I have a weird problem in some of my Unreal Levels: 
As you can see, the billboard itself cast a shadow. It happens in a few levels of one master-level I use for level switching. The most of the 12 levels are working just fine, but in a few there is this shadow issue.
Do you habe an idea what's causing this?
Thank you, best regards,
Jan
SOLVED :) The issue was not the HDRI backdrop but the directional light. It has to be set to "movable" to work correctly with billboards.
Hi,
Yes, if the Directional Light is set to static, the shadows can not change shape, which could be why you are seeing a rectangular shadow. Both static and stationary lighting are designed to be baked before cooking or playing to enhance shadow quality.
Note that you should be still able to use stationary lights instead of movable ones as they bake lighting for static objects but can cast dynamic shadows for moving objects.
Warmest regards,