This situation is terrible for me. Horrifying!
I could see the problem (hopefully the same you saw), but I can't really easily reproduce it. I believe it have something to do with adding products and caching.
What scares me most is I'm in no condition to dedicate time to this anymore. I'm not sure you are aware, but I'm no longer in this business. Still, by coincidence I saw your message as soon as it arrived. And I hardly ever leave a direct message to me hanging for more than 1 day anyway. I just didn't know what to say in this case...
Right now I can say (and couldn't in the first day) I only got to see the problem because I've been trying, little by little, to see what I can do in these past days. And I'll keep trying whenever I'm able to squeeze some time in.
This is a surprising hairy problem, even for coming up with a quick fix.