Huh! Demons it might be. Hope we get to hear the answer. 
One other possiblity…was the head moved from the home position in the upper left corner when you started the print?
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Well, there’s one other possibility, which is that the head got moved. The Glowforge only knows where the print head is when it is first turned on – that’s why it goes through that long homing sequence. After that, every movement is relative to the previous one. So if you were, hypothetically, to open the lid and push the head out of the way (on purpose or accidentally), all prints after that would be shifted however much you moved the head.
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By the way, the reason people are acting so surprised is not because we don’t believe you saw what you saw, per se. Obviously something happened, but if it’s not user error, it’s so uncommon that there are people here who have read literally 500,000+ posts on this forum and never heard of this before. They’ve probably seen every issue reported here in Problems & Support.
Could there be a weird software or hardware glitch that only happens once in a million prints? Absolutely! I work for a big tech company, we have a lot of servers, and one of the cool things about that is that you get to see incredibly rare problems. One time a computer just started doing math wrong. It worked perfectly fine otherwise, but it was making an incredibly subtle mistake that took some of the smartest people in the world a long time to track down.
But it’s probably something else. “When you hear hoof beats, look for horses, not zebras.”
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Did you work for Microsoft back then?
NOPE, it was triple checked. Placement was correct on screen and in GF itself.
I’m thinking back on the whole process as it took place. I did open the lid several times, etc. But I thought/assumed the head re homed itself each time. But YES, the head being out of place sounds more like a possibility than anything.
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Shoot! Gremlins would have been cool.
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If the head was “bumped” right by 12 inches, it would have parked in the middle of the gantry after the print completed.
If it homed back to the usual rear corner, the print occurred exactly where directed.
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I think the best explanation is that it is 2020 
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I’m creating an image on the other side as we speak. It’s engraving perfectly.; in the correct position. I do believe the head WAS bumped out of place the first time.
THANKS everyone for the assistance!
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eflyguy - it was parked in the middle! So I somehow gave it a really NICE BUMP while I was messing around under the lid. Oops, no I know!!
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To echo Jules, eflyguy, and chris1, it does appear that the head did not start at home during this print. The giveaway is the size of the offset.
Often, when we see an offset this large, it occurs because the head was physically moved or accidentally bumped, which affects the current calibration. I extracted the logs from your Glowforge to investigate the print you reported trouble with, and it looks like the printer head did not start from the “home” position. The head may have been inadvertently moved or bumped while preparing a print. I’m glad to hear that our amazing community members were able to guide you through this and that your other side engraving is going well!
I’m going to go ahead and close this topic. Feel free to reach out again in the Forum or via email should you ever need!
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