Having tried upgrading from 1.3.3 to 1.4.0-epa1, the results were that most of the config did not appear. For the reboot after the upgrade the kernel parameter "vyos-config-debug" was added.
The details (before and after) are in:-
in which I have made minor redactions to /tmp/boot-config-trace.
With apologies, I have not managed to work out what it did not like in the config, although it did make a dreadful mess!