Unfortunately, it is something that just "happens", regardless model / software / autosave.
I've had config losses on all types of switches, old firmware and recent, with and without autosave enabled. In most cases, if you miss a part of the config it has to do with forgetting to manually save the config on devices where autosave has been disabled.
Last time I had the issue was with a ERS3524GTX-PWR, running latest software in a 3 unit stack. After a reboot of the stack, configuration of unit #3 was gone. I put it back in and unplugged or rebooted a few times, but nothing strange happened..
I've read that new firmware should introduce a backup configuration to prevent defaulting if the primary config gets corrupted.
Just make sure you always have a recent copy of the configuration, in case you have to put it back in the box.