I believe that is the default setting in Simplify for the Da Vinci. I have been using the default settings with no issues and even turn the speeds up part way through most prints with no issues. I don’t think it is a power problem or a speed problem. I’d guess there is something getting in the way, are all your cables out of the way? Does this only happen on a specific print or no matter what you print? Have you tried recalibrating your bed? Also what firmware are you running?
This is common with the Da Vinci. Check the wiring going to the X motor. That wiring bundle goes through a lot of stress with the sharp bend so some of the wires tend to go bad and break the connection momentarily. This causes the motor to skip steps.
One other thing to check, that I have not seen mentioned is the bearing housings on the printer are known to crack, and known to cause play. Even if the belt is tight, there is a chance you are getting some type of backlash. Several prints on thingiverse including X axis belt tensioner with bearings for the Da Vinci 3D printer by oscahie - Thingiverse 29 may help even if your belt is tight, perhaps the gear is slipping causing backlash. Not sure but thought it was something I had not seen mentioned above.
My problem was kind of the same and it turned out to be the cracked bearing housing problem. It was driving me crazy so I took the X axis and sure enough the black plastic bearing housing was cracked. Carefully I printed one off and it is working again.
First check the hardware (belt, gear, bearing, cables) and firmware like mentioned below. It can also be a problem with the slicer in Repetier. I had the same problem a wile ago. Try it with a new g-code and try not to stress your computer to much wile slicing.
Had my 1.0 for almost 2 years. I’ve had a very similar problem, sounding exactly as you described. Nothing I tried worked, went through almost an entire cartridge before I gave up. The death sentence came when tech support advised I ship the 57lb printer to them and import it back - pointless since the whole act of shipping and receiving it exceeded the cost of a whole brand new printer by USD$100… a $400 cost I won’t gamble on. A short while ago, I ordered a different brand.