My cnc reduces speed when cornering

[SaporeCNC]

Hello everyone !!!
Before discussing my problem, I pass the components of the equipment

1) 4 motors ES-M23480 (with encoders), 4 drivers ES-D1008 and 2 sources SPS-608 all Leadshine
2) CSMIO-IP-M controller and generic 24V source
3) 20mm recirculating ball screws step 5 (on all axes)
4) HIWIN linear guides of 25 on Y and A axes (slave axis) and 20 on X and Z axes
5) Structure made of 7071 aluminum of 10 and 20mm thickness and Bosch profiles of 40x80 / ​​40x40mm
5) HY spindle from 3KW to 220V (Chinese)
6) PC with Windows XP Soft Mach3 Version R3.043.066

I describe the components as it seems necessary to expose my problem and see if someone can help me ...

cnc is underway a week ago and I'm still testing speed settings and axes movements, they are already calibrated from the mach, the machine runs through the mm. that I indicate until here everything perfect, the axes move at constant speed and even in X, Y-A and Z even if I move X and Y-A at the same time everything is perfect!

but my problem is when I load a G code (done in Mastercam X5) to make a square of 100mm on the side with "rounded tips", on the straights it is perfect in speed, but when it reaches the curve it becomes slow and starts as a Take short steps seems to stop and continues slowly ... does not make a smooth and even as in the straight
I do not know if it is due to the wrong G code or some configuration of the Mach3.

The mach in "General Configuration" I have it as in the photo that I attached, but I do not know if it is ok

from now I appreciate your time and help

Greetings to all!