So if the same procedure (with exactly the same files) reproduces reliably when using a partition and gpart --- and it does not reproduce at all, even with multiple attmepts, without gpart, then it is clearly a gpart bug.
So if the same procedure (with exactly the same files) reproduces reliably when using a partition and gpart --- and it does not reproduce at all, even with multiple attmepts, without gpart, then it is clearly a gpart bug.