Your ROOT_URL in app.ini is https://source.parasitstudio.de:63000/ but you are visiting https://source.parasitstudio.de/wirtz/esp-link/blame/commit/680edf931b65167f1a206b0429351e326a54a1f5/examples/web-server/Voltage.html
You should set ROOT_URL correctly, otherwise the web may not work correctly.