I really don't know what is going on from this description.  I have no experimental data for an anchor impeller with wall baffles.  An anchor impeller in water, without baffles should require only about 700 Watts.  An anchor with baffles or calculations with various other impeller combinations give power estimates between 1.5 KW and 3.5KW.
 
From the description provided, the problem does not sound like a mixer problem.  I suspect the problem may be in the wiring or adjustment of the controller.  Start by checking both the voltage and amperage going to the motor.  Then check the wiring against the installation instructions.  Then check the installation manual to be sure that any adjustments in the controller are set properly.  An adjustment could be set to the wrong extreme condition.
 
The real problem may be when the mixer is used for a more viscous material.
 
As a general comment:  Anchor impellers are rarely the best choice for any mixing application.  The impellers create poor top-to-bottom motion.  The combination of anchor impeller with wall baffles is even more confusing, because they would be working against one another.  An anchor is usually used to maintain fluid motion at the tank wall.  Baffles are used to prevent the rotational motion typically provided by an anchor.  This combination is extremely unusual.