Twice sold me a dud: not again! (4,3,4,3)

I believe the answer is:

same old same old

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'again' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'twice sold me a dud not' is the wordplay.
I cannot quite see how this works, but
an anagram of 'sold' is 'olds' which is present in the answer.
'me' is found in the answer.
'a' is found in the answer.
'not' could be 'o' (I've seen this in other clues) and 'o' is found within the answer.
This explanation may well be incorrect...

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I've seen this clue in The Times.

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