Using ZCM 10.2.0 on Win2003S server, XPSP3 clients

I realized that some of my PCs reinstall all assigned bundles after running
well for months, I don't know how many are affected because most of the bundles
installs are completly silent. The issue became visible when it occured on
a PC using a bundle requiring a reboot to complete the install.

I checked zmd-messages.log and did not see what trigerred the reinstall,
the only errors I see are related to concurrent access to the local cache.

Any idea where to start to look ?
In the interim I will create a bundle that will send a trap in the Install
phase to have a log of the reinstalls.