Same here on 5.8.4 (Launcher build, CL 58902052), Windows 11, 32 GB RAM, RTX 3070 Ti, so I can confirm what MEHMETMP27 reported.
In our case it happens on every build: 11 of 11, each one in a fresh editor session. We only get one of the four errors, and it reaches Python as a RuntimeError from build_meta_human:
/Game/MetaHumans/Common/Face/CR_MetaHuman_HeadMovement_IK_Proc : Cannot break link Multiply.Result.Z -> RerouteNode_1.Value
The two Face_ControlBoard_CtrlRig errors do not appear in our logs.
Our setup, in case it helps to narrow it down:
- Python through Epic’s own remote execution (Python Script Plugin), no third-party bridge
- Cinematic pipeline (MEHMETMP27 used Optimized, so it is not tied to one pipeline)
- auto-rig
JOINTS_ONLY,enable_wardrobe_item_validation=False - several different presets, not only one
Despite the error, the blueprint and meshes are created, and the characters render correctly in Movie Render Queue with a body idle animation. We have not tested facial animation, so we cannot say whether the face rig is affected.
Possibly related: in our scripted builds the editor keeps everything from each build in memory (5–18 GB per build, not released by unloading the packages and garbage collection). Your observation that the 326 generated packages stay dirty in memory fits that. Our separate report on this:
Voted. If you get the same errors, please vote as well, so that this becomes a ticket at Epic.