I'm getting this on one of my boxes too. In my case it seems that the problem is simply the NAND flash wear-out (What is NAND flash wear-out? - Definition from WhatIs.com). I've solved it by building an image which uses SD card for storage instead of the internal NAND.
I am now trying to make a new build for MX2/G18 based on LE 8.0 (thread-4858.html). I can build a version with storage on SD card of this too. Or I can share the build I currently use for my own box (based on original codesnake's OE 6.0.3 with storage on SD card and RetroPlayer 15.2 included).
It would really be appreciated if you do share the build you are using, I am having the same problem. Thanks!