I know, but I wouldn't be able to give much specifics due to privacy reasons. I can say that the common theme is dissatisfactions with the velocity of making decisions, leading to conflicts/frustration. In a large org, ICs are at the mercy of the management for velocity. When you step down from the TL position, you may feel pretty frustrated that your impact is now tied to some one else's (sometimes slow) decision. This feeling is already common between the normal ICs, but for TLs-turned-ICs, I think they experienced it much worse. All the people I knew burned out, complained about management, and left for another team or another company.