Well I see this sole difference.
So, I have a UD field (Plant_c) on ReqHead, and I think that yellow field (UD_SysRevID) is the FKV or something related.
The EFx from @Dragos has the yellow field in both rows. My EFx is missing it on row 2 of the dataset. I would guess this is causing the error.
So perhaps the insert widget cannot handle a table (View) with UD fields?