I am getting that error also.
I don’t use any reverse proxy.
If I remove my remote server settings from the app then the errors are gone.
I connect to my network via openvpn but if I don’t have the remote server settings set in the app then I cannot access the local openhab using the app BUT I CAN if I use the web browser.
I am NOT using the cloud openhab I am using my local openhab.
Also in my overview page I have web urls which don’t show up if I use the phone app with the remote server settings and I am on the vpn but they do show up if I just use the browser. It is like the app is blocking these somehow.
I guess the easiest for me would be remove the https remote server settings and just use a web browser if I need to access via vpn when I am out of the house.