I joined a company that was rapidly expanding as it spun off from its former owners, and was building out its own (really good) culture and plans for the future.
Within a couple of months this changed virtually overnight, with the company being bought and suddenly starting to lay people off. I'm working on a project that's due to complete in the next few months, and have little confidence in my long term job prospects once that's done. Which isn't a great place to be after 6 months in a role, and having recruited a load of other people based on a vision of the future that turned out to be false.