The in x360ce is almost always a symptom of a communication breakdown between the x360ce app, Windows permissions, and the ViGEmBus virtual controller driver. By ensuring the app runs as an administrator, whitelisting it in Windows Defender, and cleanly reinstalling the ViGEmBus driver, you can quickly bypass this error and get back to gaming with your preferred controller.
This is temporary; the error may return after next reboot. self protection failed error code 4 x360ce 2021