[spartanatreyu]

In recent memory, the biggest two that come to mind:

- Halo Infinite's slipstream engine turned into spaghetti code due to 343's terrible employee cycling, most of the directors left around the same week, and now they're rehiring a brand new team made up of devs with Unreal Engine experience because the old engine would take too long to fix.

- The terrible console performance and engine woes of CD Project Red's Cyberpunk 2077 that almost led to the company being sued into hell led to them abandoning their own engine and switching to Unreal Engine for their next game.