For everyone's interest, I have had a TH16 catch fire and destroy its case. You can see from the attached photos that the AC input capacitor appears to have failed and started the fire. The module was running in a 230 VAC 50 Hertz environment. I wonder if the 275 VAC rating for this capacitor allows enough "headroom" for any system transients, or whether this was a random failure. I have many Sonoff devices in use, including one other TH module with the same capacitor. Users may want to take a conservative approach and replace this capacitor with a higher rated one before putting the module into service.
This is the Nextion Forum
But I understand, you may have wanted to get that off your chest.
Thanks Patrick. That'll teach me for sitting at the screen into the wee small hours. Certainly got it off my chest, as you say. Apologies to all. Hopefully someone got something out the post anyway.