It can be due to exposure od device to radiation example like X-rays etc. It cna also be due to electric fields present in the system.
The flash is connected to the SoC through General-Purpose Memory Controller (GPMC).
Does the flash have any settings that when set to marginal values, the flash gets corrupted as described ?
Is there errata sheet for the part to check it against GPMC settings ?
I have checked our internal database and the part GL128S10DHI01 does not have any errata.
Please let us know on how many devices you are seeing the issue.
The factory just reported more 5 boards, so that total is 6 boards.