hobbit graphs

I've strange behaviour on a xymon 4.2.3 server, some of my graphs are not shown. For example, the disks graphs are not all shown. I've 7 partitions, and I can see 2 graphs containing each one 3 partitions, but the 7st - of course the most important - is not graphed. A valid RRD file is generated, data are stored, and a link is provided instead of the image. This issue is in many graphs, very often for the 3rd graph.

Any limitation for the number of values that can be handled in graphs ? Any hope it's corrected in 4.3.0 beta ?