Please note that "rebooted because of kernel failure" means that router rebooted due to unexpected situation. Could be caused by software, hardware or Watchdog. Each case must be resolved separately through support. In order to reach solution as fast as possible - write to firstname.lastname@example.org
and send latest supot file which would be generated after such crash on latest RouterOS version.
Kernel failure is not one specific crash. At the moment we are not aware about any current software caused Kernel failures. If we would receive complaint about software caused reboot, then we would fix such issue as soon as possible.