some data isn't stored in RRDs unless --debug option used for rrd-data, rrd-status workers

Not sure if this is a bug or just something weird in our environment,
but I've run into a situation where some bits of data aren't being
stored in their RRD files, causing small & big gaps in the trend
charts.  However, if I add the --debug switch to the rrd-data and
rrd-status workers in the tasks.cfg file, the problem seems goes away.
 Has anyone else observed this?

I'm running xymon 4.37, rrdtool-1.2.27, and the OS is centos 5.7 with
kernel 2.6.18-274.17.1.el5PAE.

I'll be glad to provide more details, back traces, etc.

Any help is appreciated.

Thanks,
Tom