As the "second-generation" proof of the Classification of Finite Simple Groups is being written up in the volumes by Gorenstein, Lyons, Aschbacher, Smith, Solomon, and others (see e.g. [this question](https://mathoverflow.net/questions/114943/where-are-the-second-and-third-generation-proofs-of-the-classification-of-fin)) certainly much of the work will go into fixing minor (and possibly major) issues and gaps in the proof, since the first announcement in 1983. 

Here are two such gaps:

 1. The classification of quasithin groups. G. Mason claimed a proof in an unpublished manuscript in 1981, but this was found to contain serious gaps. It would not be until 2004 that this gap would be fixed (see [this behemoth](http://homepages.math.uic.edu/~smiths/papers/quasithin/quasithin.pdf)). 

2. In 2008, Harada and Solomon filled a minor gap in the classification by describing groups with a standard component that is a cover of the Mathieu group $M_{22}$, a case that was accidentally omitted from the proof of the classification due to an error in the calculation of the Schur multiplier of $M_{22}$ (from the [Wikipedia page for CFSG](https://en.wikipedia.org/wiki/Classification_of_finite_simple_groups)).

I would like to see a longer such list! Thus:

**What other (major or minor) gaps have been discovered, and subsequently fixed, in the proof of the CFSG, since the announcement in 1983?**

Of course, if there are any gaps that are "known, but with a known fix" (but which have not yet made it into the aforementioned second-generation proof), then these would also be interesting to know.