preOpenCard not running on iPhoneX simulator

[Alan]

I'm having a strange issue with a mobile app - on the 11.2 simulator a preOpenCard handler doesn't seem to run on the iPhoneX simulator but does with other devices.

What might be stopping this handler from running on the X simulator but not on others? Any ideas?

Strangely, when I make a barebones test stack with only a preOpenCard handler, it runs ok on the X simulator. So that points to something in my original stack... but  what can stop the preOpenCard message from being sent??

cheers

Alan