Appium unable to find UI-Elements using XPath - selenium

Question

I need to find UI Elements within my Windows Desktop WPF application using xpath and Appiums xpath-selector.
It's working fine for "simple" applications but fails for my target application.
My environment is:
OS: Windows 10
Target Application: x86 WPF
Appium Windows Driver: 4.0.0.6 beta
Appium Desktop Application: 1.13.0
Selenium WebDriver: 3.141.0
This is what I am trying:
Once I have fired up my target application by the Appium desktop application, its session window tells me the xpath to UI-elements, such as (also see the screenshots):
xpath:
"/Windows/ToolBar/Tab/TabItem[1]"
Appium Session Window Screenshot:
Microsofts inspect.exe screenshot:
The wired thing now is:
If I am using the xpath-string that appium shows me, in order to find the corresponding UI-Element within this session manager itself (by using the search-feature and selecting the xpath-selector), it's unable to find any elements (see screenshots):
Also, if I am using a trivial xpath-string such as
"//*"
or
"/Window"
it fails as well by not finding any elements.
Here, as a contrast, are the same steps captured by screenshots for the baretail.exe notepad application, for which it works, i.e. where I am able to use the provided xpath-string to correctly find the corresponding UI-Element.
Appium Session Windows:
Microsofts inspect.exe:
Appium Session Window search for UI-Element - query:
Appium Session Window search for UI-Element - result:
Eventually, I need to use this from within a C#-project, for which I am using the following code, but i am getting the same result, which is, not finding any UI-Elements matching my xpath-string.
(I debugged the Appium source so far that I already know that the FindElement-request using the xpath-selecotr is submitted successfully, but the Appium server responds with an empty result set of found UI-Elements.)
AppiumOptions options = new AppiumOptions();
options.AddAdditionalCapability("app", "path/to/my/target/application");
options.AddAdditionalCapability("deviceName", "WindowsPC");
options.AddAdditionalCapability("platformName", "Windows");
options.AddAdditionalCapability("newCommandTimeout", "60000");
session = new WindowsDriver<WindowsElement>(new Uri(WindowsApplicationDriverUrl), options);
Assert.IsNotNull(session);
session.Manage().Timeouts().ImplicitWait = TimeSpan.FromSeconds(1.5);
string xpath = "/Window/MenuBar/MenuItem[2]"; // valid xpath to an UI-Element
var result = session.FindElementsByXPath(xpath); // successfully returns an empty collection
Anyone, any ideas? Please ...