RTOS/OMAPL138B-EP: Interrupt of EMDA is not trigger to OS

Part Number:OMAPL138B-EP

Tool/software:TI-RTOS

I am developing application on OMAP L138 processor using EDMA, my OS is SYS/BIOS 6.45. I have met problem with trigger of interrupt of EDMA, when it's running, interrupt is happen approximately 20-30 times, and then no interrupt happening. I has checked IPR register of EDMA and McASP and flag is set, but OS does not call to Handle function of this interrupt. I don't know why. And this problem is not often happen, 50% times when I run application, can you explain my problem. Thank you so much !