It also has a lot to do with the breakaway torque, Sandro. Depending on how your diff is set up, there may not be THAT much torque bias in the spring plates. In fact, most retail-available LSDs are intentionally setup with minimal spring pressure so that they're streetable (think the logical extreme: the welded diff). My NX's clutch-type LSD would always spin free when I hopped curbs; your recent experience simply affirms that limitation to be expected from street LSDs.

For racing applications, it's very important to consider re-springing your clutch packs to better suit the racing environment, assuming you have the knowledge/experience base.