How the heck does this happen?

I started my print and while printing the first layer of the raft, it appears as if every other line (traveling from northwest to southeast) the printhead is lower and not allowing the filament to extrude. Traveling the opposite direction (from southeast to northwest) seems to be doing fine. Has anyone seen this before and what could possibly be the cause?

Is there some freeplay in the X axis - if you move the toolhead with your hand side to side or front/back is there a feint wobble detectable? If so, you need to follow the FAQ and disassemble your module and tighten it internally as the rollers have shifted and are not putting pressure on the guide rails.