E.g.:
"... with all the sustainability considerations that that entails."
If I'm correct, the above example is relative pronoun followed by pronoun - it just happens to be the same word for both grammatically legitimate, albeit adjacent words.
Or, even an example with three that's in a row:
"It wasn't that that that was referring to."
The above sentence may even sound natural in common speech if delivered fluently and in a context in which it was fully understood.
So if one accepts grammatical correctness and one is being clear in it being known what the examples of that are adjuncts for, are repeated that's acceptable after all?