My printer can't print complicated models

Hi i got a very weard problem. I can print simple thing like a simple iphone case without a problem but as soon as I add a name to it (cut out in the case) the printer messes up on the Y-axis en jumps higer or lower and continues printing there.
Any ideas how to solve this?

Maybe you can show some pictures ?

this was the simple good print
https://drive.google.com/file/d/0B3vumF4Al668VVR6YTN3M0IwQ28/view?usp=sharing

and this was exact the same print only with a name cut out
https://drive.google.com/file/d/0B3vumF4Al668SkRmT0RlN0l1MzQ/view?usp=sharing
as you can see on the second print it jumps to the wrong location and messes everything up

[quote=“SlowFoot”]It is beveled you can get shifts from slow or interrupted USB communication, try the same print from a SD card. But you might still have some misalignment in the X-Y axis left.[/quote] all these print where done by an SD card

Your printer is probably operating at the edge of skipping steps and the simple case doesn’t pose as much fast movements as the one with letters and that way it doesn’t skip. But as soon as you add geometry (letters) some faster travel moves are probably required and then it skips. The only way to remedy this is to recalibrate/realling the X/Y carriage and lubricate all rods.