Makerbot 5th generation leveling problem

I always find that my back left corner is a bit too low, and the raft on that side will curl. Usually this causes the bottom surface of my parts to be curved slightly at that corner. I can observe on the raft that's printed that the front right corner prints very straight lines, while the furth back and to the left i look, the initial raft layer beads as the filament is extruded from progressively higher z-distance.

I believe i can manually account for this by adjust the leveling nobs, but i'm wondering if there are any known causes for this or settings i can adjust on the printer.

For reference, the levelling process checks a "first position" and "second position". Considering the "first position" to be the "front" and the second position to be the "right", it's the opposite corner, the back-left, that tends to be too low.

Is this a "z-axis offset" thing I've been reading about?

Moderator note: First post approved! Welcome to 3DPrintBoard.

try to run Level Build plate again. This time without tighten knobs at the begining of the process.
If this doesn't work for you, then simply try to manualy level plate by printing some simple pattern on it while you are tighening or releasing knowbs.