Update for those who are interested:

The KMC X101 finally arrived on the morning of our departure to the Retroronde. The bikes were already in the car, so I decided to leave well enough alone and bring the KMC along as a spare. A visual inspection of the repaired PC-1 had yielded nothing out of the ordinary.

Anyway, it survived the gruesome Belgian cobblestones of the Retroronde, where other stuff came off or rattled out of adjustment, as well as mashing up the famous Koppenberg during a pre-ride test, where mrs non-fixie had her 'Skibby moment':



It didn't miss a beat during a three-day tour in the rolling hills of northern France, near de Pas de Calais, where, BTW, the weather was clear enough to see the white cliffs of Dover on the other side:



And it didn't protest under the clunky shifts of the Allvit while negotiating the hills and the white roads of the Peak District during Eroica Britannia:



I will be keeping an eye on that chain, but I think it's safe to say that the repair was successful, and for the time being the KMC will stay in its box.