I pulled the last failed unit this evening and feel pretty lucky, actually. The outer casing was completely melted and charred around the heat sink. Since the module was obviously dead, I dissected it and things were way worse than outside. The triac was charred and cracked and the plastic casing black and very brittle. The board it was attached to was black and fell apart when removed from the casing. One of the capacitors (c1 if you have a schematic) was inside out.
Basically, the module failed just soon enough such that it didn't burn down the house. The lesson to take away from this? The module says it's good for 150W Max...don't double that!
The only good thing is that I found a better way to disassemble these so they are more likely to be reassembled. If you have a soldering iron and desoldering iron, you can remove the solder on the tip, the two sides (just above the threaded section), and the solder blob inside the female threaded region. After these are removed, the whole thing will slide apart without damage to the circuit or casing.