OBS itself is solid. But when you add plugins of varying quality......
There's also the possibility of hardware failure, which may only affect OBS because it's the only app you have that uses it that way, but technically any app that uses the bad hardware that way can crash. That's somewhat rare, but not unheard of.
Similar with drivers, especially proprietary ones. Even the big names have released some unstable drivers. Depending on the intricate details of how the driver is written and how OBS interacts with it, a driver crash may take OBS with it, or even the entire machine.