It's exceedingly rare, but periodically we ship a unit where the lock core is not fully locked into place – the lock core falls out when you try to install the alarm. We will ship you a new lock core and a core change key, but this will take several days. If you prefer not to wait that long, these instructions show you how to fix most cases immediately.

What happened?

The lock core is held in position by the sixth "wafer" the one farthest from the front of the lock core. This is called the "core retaining" wafer. Usually the problem is that this wafer wasn't fully locked into position. This is fixable using this procedure.
In rare instances the spring which pushes it into position is missing or compressed. In these cases the last wafer will feel very loose. This you can't fix with this method, and we have to send you a new core.

What you need

A  plastic coffee stir stick, a pair of scissors, and either a hammer or some tool you can use as such. (You won't be hitting hard – just something hard that can provide a bit of impact force.)
If you already have a core change key, or if we've just sent you one, then you don't need the coffee stir stick. Just follow the same process you see here, but using the core change key.
This is the lock "core" that has fallen out.
Trim one end of the coffee stir stick like this.
So that it has a bit of a point.
Insert the pointed end into the lock. Some stir sticks have a slight "V" shape cross section, so you may find one way fits in better than the other.
Push the stir stick as far as you can into the lock. You need to retract that 6th (last) "core retainer" wafer shown here.
Before you try to insert the core, make sure the cam at the back is in this position. Hold it there while you insert the core.
Insert the core. You MUST insert the core exactly this way. (See also photo #8.)
Push in all the way until it's flush with the surrounding shell.
Almost done...
Take a hammer and give the top of the lock a solid knock. This helps ensure that the "core retainer" wafer firmly sets into position. If the core falls out again, we suggest you try the same process. If you have repeated problems, let us know and we'll replace the core.

We make small LOUD anti-theft alarms that thwart, frustrate, and stop theft of TV's / televisions, projectors and PCs / computers / iMacs. Deployed by commercial users world wide – universities, colleges, hospitals, restaurants, hotels, business centers, and community centers. Sonic Shock anti-theft alarms are not only proven more effective than locks, cables, or tie downs, they also spare your site from unsightly cables, locks, or chains that tell your customers both that you don't trust them, and that your site is potentially unsafe.