I think someone else said that all there slits didn't fire either. Personally I don't really care I like the cute thing and it works for what my intended use is. It cools enough and gives moisture.
So with the boiling issue if you put it in water and let it heat with the water I don't see why it would be an issue but I would love someone to chime in more. I know the solo people put there stems in hot chocolate which I planed on doing but my guess is it is from the start. It is never wise to put glass in water that is already boiling. If you are sticking glass in boiling water I am surprised it doesn't shatter.
The thermal SHOCK is definitely the problem so heating up the water should be safer, but I can't say definitively. It also might be better to let the water cool a bit before taking it out, reduce the shock on both ends of the procedure.
On one hand, a $50 bubbler might not be made as solid and more vulnerable to weakening. On the other hand, if something bad WERE to happen, it's only $50. Very likely you could use the bubbler for a long time, doing hot water cleanings, and then it breaks so far down the road that you will have felt you got your money's worth (and valuable learning experience)
Here's the water test/bubble video
At around
0:15 you can see the splashback up the mouthpiece.
I would say this is a medium-high water level for the piece.