not overloaded onSettingsChanged() bug with IOS ?

Have you tried it in the sim using the app settings editor in eclipse?

When your app is running, changing settings  causes a peak in it's memory usage. 

Good point, I didn't think to that !
But I test it from the simulator with the settings editor => no problem. And even if I don't have details about the user settings, the user have a Fenix 5 plus, which has enought memory (but you are right it could be a problem with Fenix5 or 5S that have only 60K...).

Use file>view memory in the sim, to see your peak.

Also, see this in the new developer FAQ:

forums.garmin.com/.../new-developer-faq

Good FAQ !

But it could not be related to a bad input of the user, because I only load settings when I init my view and it doesn't seem that the view is reinitialiazed when settings are changed. And the user says that all is right when he configures same settings with the widget off.

When settings are changed, the new setting are loaded in the app even if you don't use them, have onSettingsChanged, etc.

That's why you'll see a increase in peak memory.

I saw it, but as I said, I don't think the problem comes from it. The user has a Fenix 5 plus, which has enought memory. I'm waiting for the log, it could tell me more ...

Have you checked to see if you see it with ERA?  Might be other users have had it happen too.

Waouh ! I didn't know this tools !  What a powerfull tool !
So, it's not the only user, but it's very very strange ... it report an "Unexpected Type Error" on the last line of this code :

var display_releaseMessage = false;

...

class APICallApp extends Application.AppBase {
    function initialize() {
        AppBase.initialize();

		// Version check, message, migration ...
		if (! AppBase.getProperty("Version").equals("1.2.3")) {
			// Display a release message ?
			display_releaseMessage = true;

Very strange ... display_releaseMessage is a global var... I don't do a "+"/compare/concat or whatever, I just set the var to true...