I'm a bit frustrated with Navico (Lowrance, Eagle, etc) right now. My Eagle 500c died and was a "bit" out of warranty, which is frustrating since I am in Alaska and have a really short fishing season. Old unit probably had less than 20 hours on it and died. Navico did me right by replacing with a Lowrance unit. However, the built in maps for Alaska are horrible. Again, Navico did me right by putting me into a Elite 5 Gold, which has the Navionics Gold maps included in the package. However, very similar problem to yours. Map data is inaccurate at best, and much of the information northeast of my town of Bethel, Alaska on the Kuskokwim River is either "off", or completely missing. My unit works great with the sonar and GPS combo, but I find myself relying on my old tracks to navigate to my favorite fishing spots. If I go somewhere else up river, I might as well be driving blind because the GPS maps are useless.
Unfortunately, my old Freedom Maps (which aren't compatible with the new unit) were at least 50 percent more accurate than my current Navionics maps, which are 100 percent inaccurate.
As much as I would love to stick with Navionics, I am afraid I am going to have to switch to some other vendor. Not sure who supports mapping for Alaska, but I suspect they will be the same company that supports your needs in Canada. I understand the frustration of not having at least some level of accuracy in our maps, especially when those in the lower-48 can get the latest update of the newest Starbucks every 72 hours.
As I am doing my research, if I find a vendor that supports Kuskokwim River and Yukon River mapping well, I will post my findings here.