1) Should there have been an OSI applied on your return journey?

[...snip...]

Fenchurch Street NR exit 15:32
Liverpool Street LU entry 15:45

I deliberately phrased my points as queries because of my incomplete
knowledge of the subject and I think I may well have been wise to do so as I
now believe the answer to point 1) may well actually be NO. Looking at
http://www.dragondark.co.uk/osi/osi.pdf, which gives a recent list of out of
station interchanges (and is consistent with other lists), there is an OSI
shown between Fenchurch Street and Liverpool Street NR, but there is NOT one
between Fenchurch Street and Liverpool Street LU. It seems if you are
changing to the underground from Fenchurch Street you are actually expected
to use Aldgate, Bank, Monument or Tower Hill.

So I think you were actually charged correctly for that leg of your journey,
with just the inconsistency (in your favour) over a £9.40 cap seemingly
having been applied when the fare tables online suggest it should have been
£9.50.

So that seems to only leave the question of whether your journey from
Ockendon to Fenchurch Street should have had the railcard discount applied
to it. I can't immediately think why the answer would be no.

G.