O.K., that was just some misunderstanding.
Please always include three digits for correctly identifying a SailfishOS release (branch), or Jolla / @jovirkku will likely come to the same conclusion.
And I explicitly used sfos-upgrade and relied on its intelligence.
Which in turn relies on Jolla to provide correct information, which they prevent programmatically and regularly fail to manually. 
This is why I ultimately changed my policy which SailfishOS releases are treated as “stop releases” by sfos-upgrade, though just 16 days ago.
At all times the releases were the same.
And the clash was for the X at different releases.
And it worked at the third try.
Good, so you have not been affected.