Partly concur with Ken & D-IFF here...
The KC-30A/MRTT used by the RAAF and other nations is likely a rather different beast internally to what the USAF had specified for the KC-X/KC-46A.
The Pegasus is also very different to the Japanese and Italian KC-767s. Its troubles to date appear to stem from it's internal config/wiring/integration/software and the USAF's long term plans to fully 'missionize' the aircraft, rather than from any technical issues with hardware, although its boom does have developmental elements which are yet to be tested. I hope the outer wing flutter issues found on the Italian tankers have been addressed in the KC-46's design.
And an update: While the A330's ARBS boom has had its troubles - two are on the bottom of the Atlantic - UAE and Saudi have been using it for about 2 years including in ops over Iraq/Syria, and the RAAF has just certified it and started clearance trials this month.
F/A