Display bug from firmware update or SDK? Fenix 6x Sapphire misreporting screen shape (probably)

I have three products that all use logic based on screen shape and obscurity flags to layout the screen.

They seem to work well until I released an upgrade recently... changing SDK 3.1.5 to SDK 3.1.6 despite the known issues in debug environment because I wanted to support the newer watches. This immediately resulted in a bug report from a customer. So I downgraded to SDK 3.1.5 and the bug persisted.

As the identical (seriously) code used to work and now doesn't with both the newer and the older SDK, I have to put this down to external factors.

The customer confirms that there was a system update between his using my DataField and his noticing the bug. Therefore, it looks probable that the firmware might be at issue.

For reference, the following conditional breaks on Fenix 6s Sapphire and didn't previously..

var settings = System.getDeviceSettings();

var isSemiRound = settings.screenShape == System.SCREEN_SHAPE_SEMI_ROUND;
if (!isSemiRound && obscurityFlags == (OBSCURE_RIGHT | OBSCURE_LEFT | OBSCURE_BOTTOM | OBSCURE_TOP)) {
 // THIS SHOULD MATCH THE FENIX 6S
} else {

  // THIS SHOULD NOT MATCH THE FENIX 6S

 }

The code is misreporting so that it displays for a square layout when it should display for a round one.

I am at a loss to know what to do here. 

PLEASE HELP!