Android app connecting then crashing

I would appreciate some help, please:

Some background:

I have HA Version 21.5.1 on Hyper-V on a Windows PC. I also experimented with an Oracle VM, where I got the same result:

There are 2 phones connected to the server via DuckDNS (A Xiaomi Max 3 and a Samsung Note 3). Almost everything with my setup is working just fine. The Xiaomi phone is also connecting to the server 100%

The problem: The Samsung Note 3 connects to the server, but there is an error within a few seconds, then the Android app can no longer connect. I get the following error on the server log:

2021-05-08 20:55:37 ERROR (MainThread) [frontend.js.latest.202105040] https://xxxxx.duckdns.org:8123/lovelace:1:42 Uncaught TypeError: document.getElementsByTagName(…)[0].computedStyleMap is not a function.

I have tried clearing the app’s data. I have uninstalled and re-installed the app from the Play Store. I tried connecting via wifi locally or via data remotely. I have restarted the PC. I cleared browser cache, The same error is logged every time. However, if I connect the Samsung phone via the Chrome or Opera browser with exactly the same DuckDNS address, it connects just fine, but obviously I can not monitor the phone’s sensors via the web browser.

It seems like my install is ok, including the DuckDNS and DNSmasq configuration, because the Xiaomi phone connects 100%. What am I doing wrong???