Was able to narrow this down to a small block of code:
Using oFS As New IO.FileStream(path:=sPageImage, mode:=IO.FileMode.Create)
oPage.Resources.Images.Item(1).Save(stream:=oFS,
…...Stream, System.Drawing.Imaging.ImageFormat) The...Create) oPage.Resources.Images.Remove(oPage.Resources.Images.Item(1))...