We bumped the repo version to 12.80.6 about 3-weeks ago: https://github.com/LibreELEC/LibreELEC.tv/pull/11036 so it makes no sense that a nightly image from 3-days/nights ago would still be looking for the 12.80.5 repo (which no longer exists).
Two suggestions (in sequence):
a) Update to the latest nightly image.
b) Stop Kodi, rename /storage/.kodi to /storage/.kodi-old, restart Kodi. This gives you a clean install .. do you still see the same behaviour? If no, stop and copy back bits of config that you need, and continue to use the newer instance. If yes, put Kodi in debug mode and then run "pastekodi" after rebooting and share the URL.