jsf 2 - c:forEach does not show data in correct order after ajax update -

i m using jsf2 primefaces , have refresh problem.

i have :

<p:commandbutton ajax=true update="tableauobservatoire"

<p:outputpanel id="tableauobservatoire"

into p:outputpanel have <c:foreach... construct à table

when arrived on page, data correctly show.

when click on commandbutton, action launched, , refresh ok, table, data not correctly ordered!! if click again on p:commandbutton, data reorganized! don't understand happenning.

does need don't combine p:outputpanel c:foreach? , use combinaison in case?

if want more precision answer, don't hesitate ask me.

thanks lot!