Based on suggestions here, it looks like the workaround for my Z-Wave switch rule inconsistency issue was to change the rules that were occurring at the same time, to occur 5 minutes apart. The following day after the change, all rules worked. Before the change, I would only see a completely successful rules day, maybe 20% of the time. So far, rules have been 100% after 3 days - with no garden floods and no missed security camera feeds.
For for disclosure, after the initial 1 day successful test, I also changed my NTP servers from the default to the US ntp.org pool, as I believe this is just a better configuration for me. I don't believe this was causing any issue as my A+ time was always spot on whenever I checked.