Glad to hear there was a working solution found and luckily it was as simple as getting rid of pesky settings. I'm unsure why the models were not first tried with the default settings. I believe my original post indicated things were working fine without messing with the aforementioned settings.
As to the model size, mine still works (recently revised last month) for an 8-story high rise building with stair pressurization. Not sure if that qualifies a big enough, but certainly proves to me that FDS is going the right direction with regards to how to work with the leakage function. And of course using it for large buildings, although CONTAM is still my program of choice for many reasons. Mostly time and expense.
If the models are working without messing with specific functions, why would one state there is an issue? I have read and re-read the user guide about 100X in my career. When I first built these models, I had not read carefully enough to catch the need to define zones. Then, if you read the thread, everything worked fine after that. Unsure why the new post used specific settings, but like most software, you need to relax, not constrain, the models and simplify, simplify, simplify.
The best part of figuring this out a few years ago is that it set precedence in my area for how to set up FDS models regarding passive smoke protection. The results were quite comparable to CONTAM results.
Glad to hear there is a new Beta version coming out. Can't wait to try the old model and see how it works out.
Thanks for all the help from the NIST/JH folks, you know we all appreciate your efforts and admire your handling of these posts.