I had this issue with my submission to Mac AppStore. The final package contains two extra binary files that are not covered by the entitlement that declares app sandbox. The upload will fail with a mention of two file paths that are not sandboxed.
I personally worked around by simply deleting those binaries. My game was a single player only and test the final package worked just file without those two binary files.
Here are the two extra files mentioned above:
- {PROJECT_NAME}.app/Contents/UE/Quad/Binaries/Mac/{PROJECT_NAME}_Mac_Shipping
- {PROJECT_NAME}.app/Contents/UE/{PROJECT_NAME}-Mac-Shipping.app/Contents/UE/{PROJECT_NAME}-Mac-Shipping.app/Contents/MacOS/{PROJECT_NAME}-Mac-Shipping
Looking at the repeated path pattern. I guess this is a bug in the built in package script/tool?