When you updated you kept all settings and packages.(I never check this option and let it erase and load fresh every time.) I then install luci manually add back packages and use a saved config file. I now its annoying and takes some time but I never have a issue with updates. I guessing something has happened to iproutingtables. Maybe alzhao might have a better take on it. May try reverting and not keeping settings and packages. Then update or wait to hear from alzhao