I am posting this to clarify the position following the differential checks that were carried out on Saturday.
Both differentials that failed on initial test were subsequently found, variously (1) in a second test and (2) on detailed strip-examination in the presence of the series eligibility and chief scrutineers to be entirely legal.
In the second case [the stripped diff'] the 'problem' was found to be a mechanical failure of the offside output shaft.
In each case report were provided to the Clerk of the Course and in each case the competitors qualifying times and grid positions remained intact although the competitors elected to start differently.
Although unlikely to read this posting, I would like to thank the Officials of the Meeting for the completely professional way they handled both matters.