QtWebEngineView not loading Leaflet basemap after upgrade to 6.2.4

In my project (https://github.com/LukasBommes/PV-Hawk-Viewer) I am using leaflet.js to display a map inside a QWebEngineView. From PySide 6.2.4 (inclusive) the basemap leayer is not shown anymore. I installed PySide 6.2.1, 6.2.2, and 6.2.3 and it works fine. However, with version 6.2.4 and 6.3.1 the basemap layer is not shown anymore. This behaviour is reproducible, i.e. when installing <6.2.4 the basemap is shown again (hence I rule out a setup/environment issue).

This is the index.js loaded in the QWebEnginePage: https://github.com/LukasBommes/PV-Hawk-Viewer/blob/master/src/index.html

And here is the setup of the QWebengineView: https://github.com/LukasBommes/PV-Hawk-Viewer/blob/d83bb4111ac3bc69f82853f91ee28284a01072c4/src/components/mainwindow.py#L57 (index.js is loaded in line 173)