Well that's certainly enlightening, and concerning for me. Thanks for taking the time to explain! Might be running some memtest in the near future. lol...

Posting after having a discussion on reddit.
https://www.reddit.com/r/factorio/comments/1odm550/is_this_a_bug_or_am_i_stupid_why_wont_my_nuclear/
I was expanding a 'grid' of Substations and robo ports. I let Factorio run and was away when the issues started.
When I returned, all structures that ...