CC3200 FreeRTOS periodic timer not working properly

Hi Ti Engineer：

I am using CC3200 and do my job based on wifi audio application, in my job I want to start a timer periodicly, but from my test result the periodic timer not working properly, would you please help have a look at it. below are my code:
1. in main thread I init following two timers, TIMERA0 is one shot timer, TIMERA1 is periodic timer

    Timer_IF_Init(PRCM_TIMERA0, TIMERA0_BASE, TIMER_CFG_ONE_SHOT, TIMER_A, 0);
    Timer_IF_IntSetup(TIMERA0_BASE, TIMER_A, TimerA0Handler);
    Timer_IF_Init(PRCM_TIMERA1, TIMERA1_BASE, TIMER_CFG_PERIODIC, TIMER_A, 0);
    Timer_IF_IntSetup(TIMERA1_BASE, TIMER_A, TimerA1Handler);

in the TimerA1Handler(), I clear the TIMERA1's interrupt like below:
void TimerA1Handler()

{

    Timer_IF_InterruptClear(TIMERA1_BASE);

    ... ... ... ...

    ... ... ... ...

}

2. the TIMERA0 is working properly

3. I start the TIMERA1 in network thread like below(start it before network thread enter the deadloop)
   Timer_IF_Start(TIMERA1_BASE, TIMER_A, 60000);
   
4. But from test result , I saw below problem:
   1) the TIMERA1 timeout less than my definition(in above definition, I expect it expire each 60s interval)
   2) the TimerA1Handler() being called at random time, sometimes 12s, sometimes 6s, sometimes 60ms, sometimes 20ms ..., in general, no regularation