Crash on iOS when downloading and inserting in Database - codenameone

Question

I have a problem with my application on iOS only (iPad 9.7" 11.3.1), it works perfectly on the simulator and on Android device.
When the app is launched for the first time, the user has to log in. This works fine. After that, the menu form is launched and a Dialog is shown on onShowCompleted():
if (!Preferences.get("download", false)) {
dialog = new Dialog("...");
dialog.setLayout(new BorderLayout());
SpanLabel label = new SpanLabel("...");
dialog.addComponent(BorderLayout.CENTER, label);
dialog.show(Display.getInstance().getDisplayHeight() / 5, ..., ..., ...);
}
In the constructor, a method that downloads informations is launched :
if (!Preferences.get("download", false)) {
dlReferentiel();
}
The method :
public void dlReferentiel() {
source = DataSource.getInstance();
// I also tried with invokeAndBlock() but doesn't work
/*
Display.getInstance().invokeAndBlock(() -> requestS());
Display.getInstance().invokeAndBlock(() -> requestB());
Display.getInstance().invokeAndBlock(() -> requestZ());
Display.getInstance().invokeAndBlock(() -> requestA());
*/
requestS();
requestB();
requestZ();
requestA();
}
The requestX methods get informations from server with ConnectionRequest :
(Exemple with requestA() which needs to be the last because it disposes the dialog, it is the only one that calls the UI)
public void requestA() {
ConnectionRequest connectionRequest = new ConnectionRequest() {
ArrayList<A> as = new ArrayList<>();
#Override
protected void readResponse(InputStream in) throws IOException {
JSONParser json = new JSONParser();
Reader reader = new InputStreamReader(in, "UTF-8");
Map<String, Object> data = json.parseJSON(reader);
for (String s : data.keySet()) {
as.add(new A(s, (String) data.get(s)));
}
}
#Override
protected void postResponse() {
source.createAllA(as); // makes insertions with Transaction
ToastBar.showErrorMessage("Référentiel téléchargé", 10);
dialog.dispose();
Preferences.set("download", true);
}
};
connectionRequest.setUrl(URL_A);
connectionRequest.setPost(true);
NetworkManager.getInstance().addToQueue(connectionRequest);
}
I was able to see some logs with a Mac. Each time, the app crashes after the Dialog is shown and few insertions are made. The same error message is output :
HW kbd: Failed to set (null) as keyboard focus
Unable to get short BSD proc info for 513: No such process
Unable to get proc info for 513: Undefined error: 0
I search for informations about this issue but nothing interesting with Codename One.
I don't know what to do with this error, I tried some things like using invokeAndBlock() or changing build hints like ios.keyboardOpen (just because there is "keyboard" in it) but nothing worked.
Thanks for the help.