Also, “Canadian military tested propaganda mission on Canadians that went off the rails” could be read as the military were testing the propaganda on Canadians who as people were deemed to have “gone off the rails“. Also you can’t test a mission, you can only test an approach to achieving a mission.
How about “Snafus during in-country training exercise on propaganda techniques by Canadian military”? As close as I could get...
I was a bit cramped by the char limit, just tried to use as many words from the original article title/subtitle as possible while still retaining the original meaning
That would be "Canadians who went off the rails." It's silly to get this pedantic as long as the statement isn't misleading. The meaning is fairly clear here; even the "prey vs. pray" issue is unimportant. We all know what the author meant.
spellchecking != proof reading.