Here is a tip that may be useful when troubleshooting the TW1 lamp.

When the filament in a tungsten lamp blows, it can sometimes fuse together again while the lamp cools down (there is an example in the photo below) The lamp will then work again when power is applied, although it will usually only work for a moment. If this happens to a TW1 lamp, the lamp will show continuity across its terminals during testing, although it has in fact blown.

Note that the TW1 will not go into LAEX (lamp explosion) mode if a blown lamp only lights for a moment at power-on. This is because LAEX is only activated if a lamp lights for at least 5 seconds before it fails.