One particular Layout gets deleted (not just un-favourited) whenever we have to remove / reconnect to RDA; can this be avoided?

When we updated to v28 we noticed that one particular Layout from the Report Designer was deleted from all machines, luckily except one bizarrely, so we have managed to save it back as a favourite on all machines.

Today, we've had to remove all machines from RDA and Add the company back to all; again all the Favourites were lost, of course, which we expected but also this one Layout again disappeared from all machines.

How can we get this one to behave like the others and remain on the Layouts list?

Thanks