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In the first chapter of W. Casselman's unpublished notes on representation theory, there is at least one stated result which is not true:

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A counterexample to this last result is given in the question here. Besides Casselman's notes, I have never seen any claim of such an isomorphism for an arbitrary double coset $P_{\Theta}wP_{\Omega}$ for parabolic subgroups. Of course such an isomorphism is known when $\Theta = \Omega= \emptyset$.

There is also the result here which I have never seen anywhere else, relating length to elementary conjugation:

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The proof does not seem to come as easily as it is claimed, and I am starting to think it is not true.

The later chapters rely on some of these very carefully stated results. I want to convince myself that the important results in Casselman's notes are properly justified. Is there a known list of errata for Casselman's notes? Or another reference which carefully goes through the same things?

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    $\begingroup$ It may be worth to quote from the notes: This draft of Casselman’s notes was worked over by the Séminaire Paul Sally in 1992–93. ... Casselman has neither approved nor disavowed the end product. Casselman refers to the notes as "now out of date and full of minor errors" ... "the most egregious is the formulation of the Bruhat-Tits KTK reduction." which may well refer to the cited MO posting $\endgroup$
    – Carlo Beenakker
    Commented Jul 23, 2018 at 17:47

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