@Pils No, I didn't ask Laminar, because I don't have the problem with other planes that have the 530/430 combination. Both GNSs work normally with these. This plane is the only one (I think) that I have ever had that runs two 530s side by side. I would guess that most users are in Windows, and a lot may be using one or other of the 750s, which we Mac users cannot, sadly. Or they use the FMS.
I really wondered whether anyone else (Mac users) have come across this, but no one has said so. I'm sure Coop or Cameron have used the 525 on a Mac at some time, and if they don't see the problem, then I can certainly ask Laminar.
Anyway, thanks for coming back to me!
Note, in the screenshot, I'm fairly close to Fort Lauderdale/Hollywood International (KFLL), and both 530s are tuned to the FLL VOR 114.4