Hi, Mike and welcome.  :) You are, unfortunately, correct as the 707's current pressurization system is flawed to the extent of not being able to avoid the warnings you see. This is inevitable and therefore not caused by any wrongdoing of yours. If you follow the checklists, you can still act as if it was working correctly. That's what I do.

We've set up a list of the current issues with the 1.3 707. In case you wonder about this and that, find it here. http://captainsim.org/yabb2/YaBB.pl?num=1299594859