Issue with switch vector parameter value of a deferred decal


I’m a student in game design and new on UE4 (I usually use Unity). For a school project I’d like to detect and change color of a zone when it touches a particular element (here a blue sphere). It’s working when I enter in the first place but when the sphere quit the zone, a weird square texture appear from nowhere and I don’t know why and how it comes. So that’s why I come here and ask some help.


PS : I can’t upload more than 500KB for photos and gif, so I’ve uploaded more infos on wetransfer (here is the link : )