The specific GTAC Article on this subject is this one:
What Is The Recommended Release of EXOS For My Platform?
Which will send you here:
Release Recommendations by Platform
Looking ahead from the version listed there lands us at latest patch recommendation of EXOS v15.6.4.2-patch1-7.
I do see one occurrence of error in our internal bug tracker on a 12.5.x version, listed as "Unable to Reproduce." Generally speaking, this would be an indication of hardware failure, though it may be worth a shot to upgrade if you can.
Be careful to not void your warranty by tinkering with the components on the board, even if it is just RAM
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