low speed calculation (sensored FOC)

Since speed detection is quite poor below 15% of base speed when counting number of encoder pulses over unit time, I am trying to use set distance divided by measured time. This approach is used in speed_pr macro. Also for F28035, the eqep_pos_speed example employs both approaches for speed measurements. I am using FOC with the DRV8312 kit which runs well at speeds above 15% of base speed. To verify speed measurement, the motor is being run open loop speed control but closed loop current control at low speeds (30 -60 rpm) or 0.01 - 0.02 pu. A tachometer has confirmed the speed as well. As the motor appears to be moving smoothly one would expect to have fairly constant EQep1Regs.QCPRDLAT values. Yet, this value is all over the place and with it the calculated speed value. The QEP module has been initialized using the macro defined in f2803xqep.h. I haven't noticed much of a difference in latched period values after changing the unit timer frequency, though I think the resolution suffers as this frequency is increased. Any ideas on what might be going wrong? Secondly, do both the unit timer and unit event capture function simultaneously?