[Random under extrusion only in middle of print, perfect top and bottom]

I tried printing a known working g-code file which failed as soon as it started to do the infill. I troubleshot using this guide ->

A visual Ultimaker troubleshooting guide

http://support.3dverkstan.se/article/23-a-visual-ultimaker-troubleshooting-guide

Which pointed me to having a clogged nozzle after I checked that my filament wasn't tangled or snagged. So I performed the atomic method and it's now printing perfectly.

[Random under extrusion only in middle of print, perfect top and bottom]

Hello,

I've been using my UM2+ for months without issue until last night. A print started out great and looked like the first several layers printed perfect, as did the last several it seems, but in the middle there is a great deal of under extrusion going on. The model in Cura 2.3.1 looks good, no red in the x-ray, and the layer preview looks good as well. But why would it really under extrude in the middle but not the end? I can't figure out if this is a hardware or software issue. I have the g-code available to preview. Attached are the Cura settings, the layer preview, X-ray, as well as images of the final print. I scaled the part to 125%, used the basic Normal quality default settings, but changed infill pattern to Tetrahedral, and enabled supports only touching build plate.

Does anyone have any ideas if this is hardware or software?

The file is called Another Fidget Cube