Daniel Morgan yes that’s where TVH is installed now. Those changes to the builds were made about one year ago.
As suggested start looking through the debug logs for clues to where your problem lies. If needed post a copy here for others to examine too.
Attaching an external USB drive to your RPI should see it auto mounted and once its path is correctly defined in TVH you should have no need to mess around with permissions to get recordings working correctly.
You could as an experiment install LibreELEC on another SD card and install both the TVH client and server add on, configure them and have both a backend and frontend running simultaneously on your RPI. Again just a suggestion to make life easier.