Sometimes you may still receive ‘Hosst IPMI System Event Log Status’ alerts (which means the system event log is full) even after you reset event log and reset sensors.
In my case, the solution is ssh into the ESXi host and restart the sfcbd-watchdog service.
~ # /etc/init.d/sfcbd-watchdog status
sfcbd is running.
~ # /etc/init.d/sfcbd-watchdog restart
~ # /etc/init.d/sfcbd-watchdog status
sfcbd is running.