I had a regular template sensor that had an attribute that started with a number (probably not the best practice but whatever, it worked). I ended up converting it to a trigger template sensor and that attribute would not render. No errors, configuration passed, nothing in the log - just no attribute. On a fluke I happened to change the attribute name and then it rendered just fine.
I think that if template triggers cannot have attributes that begin with a numerical character, that this condition should throw an error in config check instead of failing silently.
Just looking for thoughts before I file a bug issue.