Application window is blank

I have a Xamarin.Mac application. Some users (probably 2-3% of all users) of the application complains that after launching the app they see an empty blank window. They don't see any text, buttons, checkboxes, etc.

Here is how it looks:

The screenshot above taken on macOS Mojave, Version 10.14.3, iMac (27-inch, Late 2013), Processor 3.5 GHz Intel Core i7, Memory 32 GB 1600 MHz DDR3.

The app is build on the following machine:

Mono Framework MDK
Runtime:
Mono 5.16.0.221 (2018-06/b63e5378e38) (64-bit)
Package version: 516000221

Xamarin.Mac
Version: 5.2.1.13 (Visual Studio Community)

Logs from the app show that other parts of the app work as expected - background threads are started, config is written, etc. So it seems the problem is related to UI part of the app.

I'm unable to reproduce the issue in my lab.

I've found the similar question here: https://forums.xamarin.com/discussion/89462/view-loading-as-blank-white-screen-in-mac-desktop-application-xamarin-mac but unfortunately the solution doesn't work for me (to move an app into directory other than Applications). The user tried to install the app into Documents directory and the results are the same.

Any ideas?