Your ROOT_URL in app.ini is https://source.parasitstudio.de:63000/ but you are visiting https://source.parasitstudio.de/wirtz/music-synthesizer-for-android/src/commit/102484e439922088dbaed5511671b3f92fa50dae/android/res/drawable-hdpi/down.png
You should set ROOT_URL correctly, otherwise the web may not work correctly.
