CL_GUI_HTML_VIEWER Display Blank page on NWBC

A few processes in our System require the user to verify an address. We had a solution for this based on Adobe Flexx, but since the support for it ended we build a ui5 application to do the same thing and deployed it as an BSP App. The site is displayed with cl_gui_html_viewer->show_url. During development we noticed that whenever we made big changes the site would only get displayed as a blank page, probably because it is still stored/cached somehwere since restarting your PC would solve the issue in the Standard SAP Gui, however in SAP Business Client the issue still exists. We ran every report / transaction from this blog but nothing helped. Does anybody know what to do?

Kind regards