It's not unpredictable, it's that you haven't figured out what the variables are. 🙂
N.B. It's basically impossible to have truly random behavior on a web page without deliberately invoking a random number generator -- and browsers' (P)RNGs weren't even random enough until recently! Of course, you can have behavior that varies based on network/server responsiveness, and those other factors can make the overall result appear to be random, but once you figure out the inputs you can get predictable output. In this case it isn't going to be related to network/server behavior. I'm sure it's down to the order in which cookies are set, stored, and reset. You shouldn't have needed my pURL fix anymore - that's one thing that tells me something is non-traditional about your testing and/or setup.
It isn't related to those Chrome warnings. (You can and should test in other browsers to rule that out anyway.)
What you need to make sure you're doing is not "clearing your cookies" but working in Incognito/Private mode and making sure all Incog/Private tabs are closed if you want a clean slate again (Some people don't understand that Incognito tabs do store cookies, as long there's at least 1 such tab open.)
Note in Firefox, when you work in Private mode Tracking Protection is on by default. You want to turn off TP while testing, because in this particular case you're using Private mode to emulate a fresh browser with no cookies, not for privacy protection.
.png)