The issue as already described in this closed question sadly still persists in 4.17:
DLC-Builds launched from Unreal Frontend reproducibly fail with 4.17 when triggered from a Project without SCM/Perforce because the staging directory is recursively marked as read-only before packaging is finished.
Iād be greatly appreciated if this issue could be resolved in a future release as this makes the DLC-Support in UE4 pretty hard to use