I recall reading that one of the two prototypes had an issue whereby the main u/c bogey, which had to sort of rotate around itself during the retraction sequence to enter the bays, failed to unwrap itself thus at leat one landing was carried out with the bogey inverted. As far as I am aware no serious damage was suffered, but it may well explain, at least in part, why ionagh has the photos illustrating differences in u/c detail.