That is false positive. Proper signature will not solve this, a lot of malware has signatures. Unreal had some false positives already. Engine “packs” or joins together multiple executables back to back, and this is exaclty same behavior as droppers and some downloaders do. As result unreal packaged files are detected.
All you can do (if you can share your project), is making thread in feedback forum, and sharing FP files with epic staff.