Deferred decal does not appear if GTAO is enabled.
1. Create a blank project
2. Create a simple deferred decal material with an input (preferably a texture sample) into the 'Emissive color' input. Also be sure to change the blend mode to Translucent. (image attached for reference)
3. Apply the decal to the world
4. Activate GTAO via r.ambientocclusion.method 1
Result: The decal no longer displays after running GTAO
Expected: Decal to still appear in the scene
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-90097 in the post.