Why do I get the message "Starting security check..."?

Every time you TP or cross a sim or login with locked cuffs, the HUD will perform a security check to ensure all your locked cuffs are still worn. If it detects a missing cuff, it will trigger re-rez , and your cuff will re-attach itself automatically.

This means that if any cuff inadvertently came off in a previous no-rez or no-script sim, the situation is rectified in the next rezzable and script-friendly sim. This will trigger the detach alarm.

This feature is fully available from HUD v5.5.2 onwards. (Initial features were introduced with HUD 5.5.0, which sometimes triggered false re-rezzes).

If you are experiencing false alarms whilst logging in to a laggy sim, upgrade your HUD. From v5.7.0 onwards, the timeout has been extended generously to accomodate laggy sims.