If this is a production system, then how are you able to do '/system reset-configuration'? Doing that would cause an outage until you reprogrammed it. '/system routerboard upgrade' would typically be less disruptive than a reset-configuration! If you are willing to run without a config on the system for a few minutes, surely you can run a 'routerboard upgrade' followed by a reboot (of course, have a spare unit standing by, but typically if 'routerboard upgrade' breaks RouterBOOT, you can hold down the Reset button while powering up the router to load a backup/failover copy of RouterBOOT, so really, there is little risk in trying the firmware upgrade).
If you are making a backup (not an export, but a backup), then running reset-configuration, and finally restoring from backup, then the act of restoring from backup will put things back the exact same way before you ran the reset-configuration, effectively making it as if nothing changed at all. If whatever is causing the 100% CPU is in the backup config somewhere, then that isn't going to be an effective test. You need to be watching the CPU while the router has no config on it, immediately after boot-up. If it is doing it while the system has a blank-slate config, then either the hardware is faulty somehow, or something in the OS itself is screwed up and the OS needs to be reinstalled (e.g., Netinstall).
If this is really a production system, I would strongly advise you to replace this router with a different one temporarily so that you can take the time to accurately and thoroughly test and diagnose the problem. If we make recommendations of things to try, and you tell us you can't do it because they would be disruptive, then we can't help you.