The Canadian Government has a long history of IT screwups. (Such as their immigration website crashing on day after Trump.)
Also Dual Canadian and other citizens MUST use their Canadian passport if they are travelling to Canada - they CANNOT travel on the other country's passport. If they don't have a Canadian passport they are screwed.
Oh, and travel via land or sea is exempt from this ETA nonsense. Fly to Seattle/Boston and take the bus/train.