Thanks to jsnbrgg for the heads ip on the X axis plug. My DaVinci 1.0a has begun sever step loss as well (X axis only). This is after flash to lucs repetier .92, but appears unrelated. Motors are not hot, nor are driver chips. I didn't believe the plug, but tried removing the right side. The missed steps were much less severe, but still present. I tried conductivity paste on the plug, and slight bends in the male pins to no avail. Finally, in desperation, I removed the motor, disassembled, removed the plug, and soldered in a solid portion of wire. My next 14 hour print was flawless. At this point, I put the right side back on - and my missed steps were back. I have removed the right side again, and am much farther into my next print with no lost steps. Perhaps it is not the plug but actual defective wires. The stock harness certainly tends to kink around the carriage at the X axis motor.
At this point, I expect that the wire will likely fail completely before long, and I will replace the harness with decent motion grade wires instead of the cheap crap that xyZprinting installed as a full motion harness.
Note that I will begin a new thread with listing this as a known defect in the da vinci printer, so others with the same problrm can find it easier...