IVR looping intermittently ( timer doesn't start for the bad call)

[avaya137xx]

Hi ,

we have an IVR message that plays at AEP
some strange issue reported by customers.

they intermittently hear the same announcement.

Bad call--- 1> when the customer made a call , they hear the announcement and it stops and again it starts from beginning.
2> on the cell phone display it shows "" calling ""

Good Call-- 1> when the customer made a call , they hear the announcement and it completes without any issue
2> on the cellphone display it shows the timer "" 00:07 " ( the timer gets started for the good call )