[Xymon] Again netapp.pl question

Hi,

I'm (still) using netapp.pl 1.21 on XYmon 4.2.2 et Data ONTAP 8.1.1P2

When my netapp.pl runs correctly, my monitored netapp has around 20 columns of green/yellow/red status icons. Sometimes, all columns are dropped except "snaplist, snapmirror, sysconfig, uptime, volume". I've planned the test each 10 min. Do you have any ideas why most of the column are 'dropped' and then, reappear later ?

Thanks.