I’ve been noticing the first 3 layers or so have a strange rippling on some of my prints. This happens on all my Taz’s (3 of them) at one time or another. I just finished upgrading the X and Z axis parts and replaced the polymer bearings with ball bearing ones on one printer but it’s still there.
Take a look at the automatic Bed leveling upgrade that 1013 made for a possible fix. The root cause of initial layer weirdness is usually caused by a couple of factors, mainly stemming from the nozzle distance from the bed. You may have the nozzle slightly too close or too far away, which is either causing the outer perimeter to not conform to the shape it actually thinks it is, or in the case of it being too close, causes it to build up plastic in the extruder and overextrude on the perimeter. As the unit goes up in layers, either condition tends to resolve itself. The problem is that the length of the nozzle changes depending on how warm the metal is. Assuming you are printing in a room that is the same temperature, you will still get a different height result from printing when the sensor in the hot end says 230 degrees C (f0r ABS) vs what you would see if you let it sit at 230 degrees for 10 minutes, because in that ten minutes the nozzle actually got 1/10th of a mm longer than what you dialed it in at. If any of your bed corners are even slightly out of level that can also compound the issue.
Additional leveling, only printing after the machine is fully up to temperature, really tight belts, extra perimiters, and ensuring your extruder is dialed in perfectly can all help with initial layer quality. Or you can print with a brim and just assume trimming will be required