Factorio Forums

1. What did I do?
I was playing with a friend inside a vanilla world trying to get the lazy bastard achievement. We were playing on his save, I joined via Steam Friends "Join" feature.
I was placing belts before I suddenly got reconnected and experienced my first ever vanilla-desync.
After reading the "How to report a desync thread I asked my friend what he was doing right before I disconnected, he told me that he unequipped his power armor and his items spilled everywhere, but he wasn't completely sure if this happened right before my disconnect.

2. What happened?
Well, I desynced and my client happily generated a desync report.

3. What did you expect to happen instead?
That no desync happens.

4. Reproduction steps:
As described above, I'm unfortunately not sure what exactly caused the desync. It only happened once and we were playing this map for several hours, currently researching rocket silo.
I'll add more info later if it happens again or find a way to reproduce it.

EDIT 1:
The second desync happened while I was pondering how I'd like to place a railway blueprint, my friend didn't do anything special: Standing around / walking.

EDIT 2:
The third desync happened while I was walking around the factory, searchring for cliff explosive, my friend was marking a train with Ctrl + C to copy it.

5. Attachments:

• desync-report-2020-11-18_23-47-11.zip (same as linked above)
• desync-report-2020-11-19_01-45-27.zip
• desync-report-2020-11-19_02-00-57.zip
• 2020-11-19_02-22-00.log (client log; ends with crash, but potentially graphics card hardware fault, so just ignore)

Those desyncs are weird, they are all related to transport lines however they are in no way near your character:
- in `2020-11-18_23-47-11` you were near copper furnaces when the desync happened on the belt with intermediates for military science packs.
- in `2020-11-19_01-45-27` you were near coal belt right of the green chips production while the desync happened on the other end of the coal belt when it was mined. That one looks like a pure single bit flip.
- in `2020-11-19_02-00-57` you were near ad hoc engine production when the desync happened near the iron ore balancer at Mine1

Without any reproduction steps i can only guess it was 1/0 magic because of the second desync.

I've tried my best to find any reproducible desyncs but wasn't able to, sorry. Also, we played multiple sessions on that map, both before and after this evening, and there haven't been any desyncs whatsoever during those times.

Good luck with finding the bad magic! Or abandon it as it wasn't a lasting issue?

Update: It probably was (evil) 1/0 magic performed by my RAM. Due to another issue I performed a memory test (memtest86) and it actually found errors even though I had checked my RAM right after installing it.

So the mystery is solved: It was faulty hardware. Thanks for your help!