Skipping layers?

[EagleSeven]

No it's definitely skipping, I've watched it on those layers and it's like it's not putting them down, I can't decide if it's the z axis having an issue or if it's not extruding well in those areas though.

Have you checked the filament-extruder drive-Gear,
to see if it needs cleaning ?
(teeth of gear can get filled with plastic,
causing filament not to feed properly)

I use an Xacto-knife and small wire-brush to clean it.

Here's a video about how to do that:
(CTC is similar to FF, your extruder may not have the Arm type assembly)
http://www.bing.com/videos/search?q=...390&FORM=VIRE7

Note: we upgraded to the spring-loaded Arm type,
since it seems a little more reliable,
even though it is a little more difficult to assemble