Unable to edit internal URL in 2.0b54

Hey all,

i just configured the app via my external URL. The Installation itself worked like a charm but when it tries to connect for the first time it just says “Loading…” and then “Unable to connect to Home Assistant”.
I checkt the connection settings and the external URL was set as the internal URL and the option “connection via” was set to “internal”. When i try to change the internal URL it isn’t safed.
Can anybody help?