I do find it surprising that this issue comes up now, The first A350 flew in early 2013, and of course had extensive testing. Qatar Airways actually had the first delivery, built and delivered at the end of 2014. That's 7 years ago, since when they have been in daily use. Surely such an issue would have arisen before now, and to the prototype more than any other. Some aircraft will have been sold on, and gone through a strip and repaint, and no longer have the original manufacturer's application. Have the earlier Qatar aircraft had a periodic repaint in their time ?