Interesting :-) I can imagine you being charged £1.30 if you hadn't in
fact been in zone 4 yet (the cap for 1-3 is the same price as 1-4) and
it
was charging you for a single covering zones 4,5 and 6 to be refunded
later.
However I don't understand why it would charge you but not let you
enter.
Surely it should do one or the other?

Was any of the travelling before 0930? The difference between a Z12 peak
and off-peak travelcard is £1.30... although I have no idea why that
would make a difference, it's just an observation!

Unless I've got confused the OP was travelling on a Sunday anyway so that
wouldn't make a difference.

If it was charging for 4,5,6 then it would have been charging the maximum
possible fare when touching in which is of interest because I believe in the
past it has been charging the minimum possible fare.