[GNC] Settings problem after update to 3.3 on Ubuntu - missing keys

[Colin Law]

I have updated a system from Ubuntu 18.04 to 18.10 and gnucash has been
automatically updated from version 2.6.19 to 3.3 from the Ubuntu repository.

I noticed that I was not getting the alternating colours in the registers
and when I went to Preferences > Register I can see that 'Use GnuCash built
in color theme' is not checked.  If I check it, exit preferences and then
go back in again I can see that the preference has not been saved.  Some
options do get saved however, Auto-raise lists for example.

On looking in gnucash.trace I see a lot of errors like
* 21:33:32  CRIT <gnc.app-utils.gsettings> [gnc_gsettings_get_int()]
Invalid key prefs-version for schema general
* 21:33:32  CRIT <gnc.app-utils.gsettings> [gnc_gsettings_set_bool()]
Invalid key use-gnucash-color-theme for schema general.register
* 21:33:32  CRIT <gnc.app-utils.gsettings> [gnc_gsettings_set_int()]
Invalid key prefs-version for schema general
* 21:33:46  CRIT <gnc.app-utils.gsettings> [gnc_gsettings_get_bool()]
Invalid key grid-lines-horizontal for schema general

and if I run dconf-editor I can see that those keys are missing.  Would I
be right in surmising that these are new keys that were not present in
2.6.19?  Is this a bug in gnucash in that it has not created those keys
automatically, or should the act of updating the package have added the new
keys, or something else?

What is the best way to recover from this?  I do have another machine with
a new install of 3.3 so I could use
dconf dump /org/gnucash
on that machine and then dconf load to load it onto the failing one.

Colin