@HolyPhoenix Thanks for catching that typo (I edited my comment, just now). I had correctly tried @psychobunny 's approach without luck but then typed it incorrectly.
I found this post from @baris (https://community.nodebb.org/topic/5942/ajaxify-variables-get-deprecated) that says the .get('name') approach has been deprecated and that this style is current:
ajaxify.data.tickettypes