I have to create a control rig in UE 5.2.1 for a CC4 character. I've been trying to use this well known method copying the UE5 Mannequin CR, however it breaks when I re-plug in the forwards solve.
I managed to discover it's looking for a spine_04 bone that doesn't exist in CC4 skeleton. It also places spine_02 and spine_03 controls in the same exact pleace, causing a weird twist. I am able to move them and fix the skeletal mesh, but after re-plugging the forwards solve, it breaks again. It looks like this:


I'm at a loss, kinda new to this.
Does any good sould know how to prevent this chest twist when using a UE5 rig copy?

Are you using the UE4 Mannequin CR ? Because you are talking about a "spine 4" and that sounds like you are using the Control Rig for UE5 Manny or Quinn. CC4 is mostly compatible with UE4 Mannequin CR.