Serial monitor window shows assertion.

I am running AnalogInOutSerial example.
only thing I have changed was delay to 800ms.

after few minutes running the example, serial monitor came up with this and halts program.
“assertion “duty <= pPwm->PWM_CH_NUM[ul_channel].PWM_CPRD” failed: file “…/source/pwmc.c”, line 272, function: PWMC_SetDutyCycle
Exiting with status 1.”

arduino due, v1.5.2 and it happens in v1.5.4
it seems working if I reduce delay to something smaller than 200ms. Anyone has idea?

OKAY. Read about map statements has bug. And this example has map function so I just commented out the function and assertion went away.