The rust at the bottoms of the doors wasn't fixed until 2014, and the weird radio glitches weren't totally gone until 2015. So yeah, it took 6 model years to get all the bugs out of the 2010 version of the Terrain.
Not positive, but I think that radio glitches were on revised stereos that were introduced after 2010. But, you're right on the doors. The '10 door sealing was probably 20+ year old methodology at the time, so I am not sure how that got past them. Hopefully they have that under control...finally.
Fortunately, GM backed up most of their screw-ups with extended warranties - either written or un-written.
I will, most likely, take a chance on the '18 though. I tend to be an early adopter - on cars, anyways. Other things, I could care less.