These are intentional, they work kind of as a "punishment" for playing for several hours straight non-stop.
The first one you mentioned is a rare random chance after playing one session for a long time, the second one appears after 6 hours but isn't directly "hostile", it will follow you around but will try to stay a short distance from you at all times so it won't touch you, it only crashes you if you touch it anyway.
The "Fatal error" crash message, if the instance of it is intentional, is typically accompanied by something else happening before it so it is quite obvious. It also slightly behaves differently than the normal fatal errors from what I have seen, the actual fatal error crashes don't seem to freeze the game after they happen.