Thanks for following up with them. They may not be having issues with lot numbers now, but when I called the first time in the spring and the rep asked me for the lot number, her response when I told her was something like “I thought you’d say that” indicating it wasn’t their first call with that number. They have been nice each time I’ve contacted them, but gave me no troubleshooting suggestions, just asked me to return them and offered new ones.
I received the Acapella Choice yesterday and it seems to be working. No blowout. I wish I’d had it when I saw RT, but at least I have something and will continue to play with settings. I’ve watched the online videos.
I also received an Aerobika with a manometer yesterday. I suspect that was your idea, so thank you.

I got sick and tested positive for Covid again over the weekend (Paxlovid/covid rebound). In a week or two, I’ll return the Aerobika.