There are some problems with LTTO that are more common than others, as well as things that every player should be aware of about their gear. If you're having a problem with your tagger, or want to make sure you know all there is to know, check out some of these issues to know how to fix or avoid them.
This can happen for a variety of reasons. The most common is that the CPU lost power for a split second due to the batteries losing contact with their connections, and is now frozen. All LTTO taggers have a Reset button on the main control panel. Some require the use of a pointed object like a pen or pencil, and some can be done with a fingernail or fingertip. In all cases, pressing the reset button clears the status of the CPU, kind of like rebooting it. After a reset, most frozen LTTO taggers work just fine. If resetting does not work, then remove and test all 6 batteries individually, and replace any that are less than 1.5 volts. Finicky taggers will need to be reset both while the battery tray is OUT of the tagger, and/or again after the battery tray is reinserted. In rare cases, when fresh batteries and resets does not work, then the tagger may be defective. In these cases, it is best to return it to the place of purchase, or contact Hasbro for customer service.
A few players have worked on simple and complex modifications to try to prevent lock-ups that occur from "battery jiggle". Check out these links if your tagger(s) lock(s) up a lot.
PartyTagger's Magic Drone Mod
PartyTagger's Battery Tray Mod
TagFerret's Battery Tray Mod
If the tagger functioned properly for the entire game, and continues to appear to behave normally, but will not debrief at the end of the game, the most likely reason is that it believes it needs to Undual from another Drone or TMB. This can ONLY happen if an eager player pulled the trigger during the last ONE SECOND of the 30 second countdown for the beginning of the game. Drone and TMB players MUST wait for the tagger to say "Good Luck!" before touching the trigger, to avoid this issue. What happens is that the tagger believes it is going to initial a DUAL mode process, but the timer runs out before it can realize that it did not get a response to the signal it sends when the trigger is pulled during the countdown. It then plays the game with full stats, but believing that it might have DUALed with another tagger. At the end of the game, it will try to UNdual (shows "UNDL" on the screen), but then give up mere seconds later when it does not get a response from a dualed tagger. It will not debrief because it believes that it only has half the stats that it should.
Just remember to not pull the trigger until the tagger says "Good Luck!" and this bug will not happen.