if_load graphs are not stable

Hi guys,

I'm using devmon to graph de interface load of cisco switches.
However I notive that the if_load rrd informatie is not always updated.
The informatie in the web pages are correct, but when i look in the rrd file, there is no update.
Also when i look in the directory i find that not all the files are updated

Anyone has a clue ?

Bert Klomp