Different PWM periods in 2xPM_Sensorless

When in 2xPM_Sensorless.c one of pwm module's period differ from that of the second, motor putted on the first pwm starts jittering, vibrating and moving slow.

Code example can be seen there:

http://e2e.ti.com/support/microcontrollers/tms320c2000_32-bit_real-time_mcus/f/171/p/96572/336997.aspx#336997

What's the problem?

Thanks.