I have create some dynamic Description properties on components, for example:
"WIDTH@BODY_SKETCH@FRAME.SLDPRT" mm x "LENGTH@BODY@FRAME.SLDPRT" mm
Length: "Length@Body@Default@BEAM.SLDPRT" mm
$PRP:"roller_type", "DIAMETER@BODY_SKETCH@ROLLER.SLDPRT" mm <- where "roller_type" is another custom dynamic property.
If I make any update from the main assembly the Component Description doesn't update with correct values, I use our own configurator add-in Tacton Design Automation to update the geometry but it is the same if I manually change anything from the assembly. I need to go in to each component and save them for the change to apply in the assembly.
I created a very small test assembly with only two components, and linking Description with Mass, Volume, and some parameters, and in that model it works. So it seems to be model specific, perhaps the size or that a lot of other things are updating?