Ok some background, i have three Makerbot Rep 1's that have been modded quite extensively over the years, no issues with any of them. I have been using Simplify 3D for about a year now, no issues.
Now this week i designed a part and sliced it with S3D and saved it to the SD card and started printing it with two printers, to double the amount i can make in a given time as i need a large quantity. The first batch was perfect, the second batch was messed up, the third was ok, then another messed up, then i did 4-5 batches with no issues, then again they messed up.
As random as it was i thought maybe it was a problem with the X axis on the one machine, since the X axis is what's shifting on both, but again two machines having the same exact drift in the X Axis on the same part? So i fired up the third printer and it printed a few batches just fine, and then bingo the same X axis drift again. WTH...
So i just selected something else at random from the SD Card and they printed those fine a half dozen times, no problem there, go back to the part i just sliced and failed on the very first try.
No settings have been changed in S3D, nothing has been changed on the printers either. I can go to files i sliced a few days prior and they work fine, but the file i just sliced is not working. I ran it through all the checks and repairs possible and found nothing wrong with the model, and the fact that it prints ok about half of the time is making me think there is something wrong here that i am overlooking, but as to what that may be i am clueless!!!
Any suggestions? The only common denominator is S3D, i tried slicing another part and again tried printing it on all three machines and again i had layer shift. So its not a mechanical issue, its definitely a software issue, just not sure what???