2+ Extended serious layer shifting

[dmitriR 0]

Ok so, Ive been using an Ultimaker 2+ Extended recently and after a big print Ive found a serious issue that has make the entire print useless. 

It seems that, around 81mm or so, the entire print layer has shifted, massively, as can be seen below. 

What are the probably causes of this issue? Is it just the servo belts that potentially need tightening? Or is there possibly another issue that I need to resolve? 
I also got an ER05 code, which has the Z-axis being broken, but I think that was due to me running out of filament, the other prints that I have done seem to be fine, but none of them approach the 80 mark

In addition to this issue, another piece that I printed is ugly and spotted with extra filment. Is there a particular cause for this? Or is it just because of neighboring prints? 

 

For context, im using 0.8mm extrusion of 3mm PLA, 20% infill

 

Thanks in advance!