G’day Jeremy.
I don’t know if this is a valid hypothesis or not, but here goes.
I have used a mail rule, which runs an Applescript, for over 9 years, without fail.
I wrote it for my Mail Manager application, which started life as a bunch of Applescripts, for Clients who utterly MUST have it work, EVERY time.
However, the rule is in two parts, the first of which takes every Email that arrives in an initially user-choosable inbox, (that the rule is then applied to), and transfers it to an ordinary mailbox, ‘* items to store’.
Only then does it call the Applescript, which it turn checks an Application set flag, stored in the Application's preference file, and determines if the script is ‘allowed’ to activate my Mail Manager App.
My thoughts are that by first shifting the Email, the Applescript somehow sets itself up as being able to reliably work. Just guessing, but as calling the script has never failed in 9 years, and been called over a million times, somethings got be be responsible!
If I’m right, Mail Rules ALWAYS work, and their being called is utterly reliable. It’s just that if the mail rules FIRST, and perhaps ONLY task, is to run an Applescript, that called script can prove unreliable in it’s activation.
Regards
Santa