@Cole D, oh yeah... I did forget about the fries from Checkers. That one, I definitely agree.
Seriously... Checkers has got some of the best fries I think I've ever had. I may go there
today for the fries... and I'm really surprised I completely forgot about their fries. I'll try to
order them completely fresh and I'll cross my fingers in hopes that they actually listen to me when
I tell them I want fresh fries. They live very close... I could literally walk there.
I may have mentioned A&W a while ago on this thread, but I don't remember. A&W is in my favorites, for their
hotdogs, and Rootbeer. Their fries are great too.

Where it can evaporate to in the sealed bottle (before first opening ?)

Yep it is an American Electric 15-000. Good eye.

Los Angeles and a number of surrounding cities still have a good number of mercury vapor street lights, and they are still maintained. Mostly cobraheads, but they also come in decorative lights. Here, where I live, two freeway overpasses have mercury soffit lights underneath. That's it, aside from parking lots.

Welcome aboard! This is Dave, do you remember me stopping by a while back and picked up the Westinghouse 1000w mercury lamps? Well, that's me and I am one of the administrators on the site.

It looks like the barium layer on the cathode was somehow completely destroyed when the thing was not in use for long time, so the cathodes had to restore it. But during that the ballast had shut it off.
The thing is the man electron emission layer is an atom thick layer of barium, which normally goes away, but it is being restored by the cathode heat decomposing the barium oxide coated onto the filament. This is, how the oxide works as the reservoir, the cathode end of life is, when there is no more barium oxide to be decomposed to restore the layer.
In your lamp this process has been disturbed by something, so it took heavier heating cycle to activate some other spot on the cathode.
It could be, the spot with the active layer formed flaked off, or the spot had already moved to one end where it runs out of the oxide and had to be reestablished somewhere else. Or the lamp is just EOL and it is really "scraping off" the remaining bits of the oxide, in that case it will be quite hard on the ballast...

There is far more then just a perfume in these fills. And because those insects are no joke in many areas, the user has to be made sure what he uses is really performing as it should. That means the thing is not degraded when used. It is not just the main active chemical what may degrade, but also the solvent have not yet evaporated, the knot is not clogged and many moredetails that make the thing work,...

Nowadays (thanks to LED) they use to be in the form of an iluminated edge of the main headlight, very often together with the turn signal (the DRL then temporarily turns off, when you activate the turn signal). So when off, it uses to be quite invisible.

The only T6's I heard of is the F42T6 and the F64T6. These were single pin lamps commonly used in display cases before the T5 HO lamps were made. Slimlines are mostly referred to the F48T12, F60T12, F72T12, F84T12, and F96T12, and of course the T8 equivalents.

I picked up a fluorescent strip light with a Sylvania F15T8/DSW bulb attached to it from Restore. The bulb appeared new. I turned it on. It lit fine for the first 2 minutes then the light started twisting and then appeared mercury starved. Then both ends glowed orange then shut down. I then tried bulb in various fixtures with negative results. Then after a while, I put it back in the original fixture and it started twisting again but it did not appear to be mercury starved this time. I let it operate for a while and the twisting gradually went away and started working normally. What caused it to do this? Both cathodes are not broken. The fixture is a single tube Lithonia with an electronic Keystone rapid start ballast. It is now working normally.