Paul Corfield wrote

There is no "not via Zone 1" for the trip you took. Gipsy Hill -
Bruce
Grove or Hackney Central is £3.10. I think you got tripped up by the
maximum journey time rule which is 110 minutes for a 5 zone travelled
through trip (Zone 3 then 2 then 1 then 2 then 3 for your journey).
The
point at which you interchanged was very close to that parameter and
I
think the OSI was probably recorded but on final exit the system went
"well he's validated all the way through but the total journey is in
excess of the max journey time so let's charge £1.50 for Hackney
Downs
to Bruce Grove". That last bit is supposition on my part

It might not be "at final exit" but rather at the point (Hackney Downs)
that the OSI touch in was checked for exceeding 20 minutes since touch
out. The test could now have been enhanced to also make a check for
maximum journey time already exceeded or so close that even a short
journey would put it over The journey time was more than 100 minutes at
this point so on a NR route 110 minutes is very close. Adding this
enhancement would not involve any other changes, just the same behavior
(start a new journey) as if the time since last touch out had indeed
been exceeded.

--
Mike D