Welcome to our forum.
....now where's that cigar your hiding....
Interesting regarding the head rests floating out. My dealer approached me a few months ago on a trade in on my AS Cub. The blemished tubs had just been released from the factory, and he wanted to know if I was interested in trading in my Cub Signature for a fully loaded 8' Tundra with an MSRP at something like 16k CAD for $12K. The catch on this tub was that the part of the shell that held the head rests in were out of dimension, and the head rests would float out. The head rests should not float out.Good call on the HS Tub...sounds like the Arctic Spa dealer you encountered may need some more experience.
I'm not buying the story about the smell in the other spa comming from shocking the spa. I've never had that happen to me after shocking. I'm guessing the smell you smelled was from the under side of the cover. It's a very unpleasent musty smell and that dealer would have certainly noticed it if he'd been checking the water chemistry in his spas