Printing trajectory ranndomly changing

So, I've been using my Prusa-i3 for some time, printed few models with it. But today while printing a model I encountered an issue never seen before - extruder starts to print in the wrong place, as if it was stuck for a few seconds, board considered that the extruder moved, and continued printing, but the layer was off. I think it's better to explain with pictures:

1 - Print started. Everything works the way it supposed to
2 - Sudden change of trajectory. Printing is few inches off it's initial placement.
3 - Another change of trajectory.

The other interesting thing is that each time trajectory changes, printer and all the fans stop for a moment.

Highlighted LED on RAMPS, the one that is continuously blinking red, stops too. But just for a split second.

I'm usually printing using Repetier Host and my printer linked to PC, so I've tried to change my approach - print from SD, since it could be something wrong with USB cable, but situation got even weirder. Once I pick the model, printer doesn't even finish heating and my board reboots - LCD display shows Marlin logo, printing is naturally cancelled.
This time another LED blinks with green light.



I have looked on the internet for similar issues and solutions, and all I've got was something like "check whether all your motor belts are tight" etc. I am really in a tight spot here, so any suggestions are much appreciated.

If everything is turning off, check if the PTC fuses on the RAMPS are overheating. Also check the power supply and connections.

Quote
stephenrc
If everything is turning off, check if the PTC fuses on the RAMPS are overheating. Also check the power supply and connections.

Connections seem to be fine - it was the first thing I did, but I had no idea about fuses. They don't overheat though - I've got fan cooling the board, plus I've held the finger near one after reading your message, but it was just warm when board rebooted

Unplug the display and see if it prints ok. My display requires too much 5v power and I had to add a 5v supply.

Guys, let me humor you - so I've been wrecking my brain trying to find the error, then my friend comes by, he says "Let's look at the PSU", I'm like "Come on, I've already checked it from top to bottom". Then he starts to unscrew it from the printer frame(for batter access to wires) and.... a small nut falls out from ventilation hole. It was the source of the problem.

Edit: I see you solved it.

Edited 1 time(s). Last edit at 07/27/2016 06:14PM by blahhh10.

Yeah... That damned nut tried to screw with me no pun intended, but powah of friendship saved me