The Net Background process runs whenever a buffer is required but is not available to the process or interface. It creates the desired buffers from the main pool based on the request. Net background also manages the memory used by each process and cleans up the freed-up memory. This process is mainly associated with the interfaces and can consume significant CPU resources. The symptoms of high CPU are increase in throttles, ignores, overruns, and resets on an interface. The crash could have happened cause of low memory on the router, but we cannot confirm anything unless we decode the crash.
I would suggest to open a Cisco TAC case so they can decode the crash and provide you an explanation why the router crashed.