Cannot add a master/detail relationship because the division and/or owner fields are in use: DatasetData: null
What sort of metadata is "DatasetData"? It sounds related to WaveDataset, but I believe I've cleaned all the Wave metadata up - as nothing there seems to reference the OwnerId field anymore.
I've done a number of successful dry runs of this in scratch orgs, but obviously those are pretty pristine compared to a sandbox.
Edit: I turned OFF analytics completely in the sandbox and the error is still happening. So much for that hunch?