I didn't expect the switch from MLC to SLC NAND flash to make any significant difference to reliability, but I seem to have been wrong. Just had another device (with old MLC chips) randomly lose all its settings upon reboot due to a flash read error. Haven't heard of any problems of that sort since the switch to SLC (though maybe I just missed it somehow).
The problem is, that isn't supposed to be explainable by flaws in MLC itself. We're hardly loading the chips at all, and being very careful to avoid writes whenever possible. Maybe it was a bad batch of chips or something...
(Also, the Linux kernel's ubifs is completely terrible at handling bad sectors.)
ssh+2FA to all your machines, anywhere, without opening firewall ports.