Hello,
after fixing the update I can confirming that the update is now rolling and installing.
Device : Samsung Ativ S (GT-I8750),
Purchased in Germany,
device is unlocked and without operator branding,
[device is used in US and Germany]
one question : at the Microsoft store the app >windows phone insider< is not listed anymore, either German or US localisation.
researching result : standard answer by the store ...not avalaible for your device, try updating bla bla bla...
any ideas so far ? Fixing / updating this app is planned / on the way ?
btw :
thx for the good and fast solving this issue ! Well done !
Best regards
post scriptum :
...my error by failing with the update was 0x80188308.
JFYI