Why chart is flashing?

[omid5ive]

Hi

I have a bar chart with some dimensions like blow:

=if( user=QVUser() and Burjas_Miladi>=t_month and Burjas_Miladi<=n_month,Burjas_Jmonth_InLetters&Burjas_JYear,null())

(my dimension is group)

i have a problem with this chart

my chart is flashing all the time and its not good for my client

dose any one know how can i solve this problem?