In the Midwest (Rustbelt) this is a common problem on rear wiper blades of basically all manufacturer's, and is caused by corrosion on the wiper arm hinge pin. So, in this case at least, Toyota doesn't seem to be the only manufacturer with poor design engineers.
The corrosion prevents the spring from pulling the wiper arm against the glass tightly enough, and usually at the end of the arc, the convex glass shape causes the (flat) rubber wiper to lose contact with the glass, at far end of the blade.
I have spent many an hour trying to fix this problem on my '87 4Runner (whose wiper reaches down from the fiberglass top, but has this same problem, as does my '97 FZJ80). C'mon, manufacturers, please care what happens to your vehicles after they leave the lot!

hahaha I'm so naive.
Anyway, the first answer (I think, I haven't completed my accelerated aging test to prove this quantifiably heehee) is preventative maintenance: keep that pivot point lubricated. I've randomly alternated between any cheap equivalent to WD40, and graphite lube like "Drop'l Doo". So far so good on my 4Runner replacement, and my wife's Venture.
For those of you (like me) who don't think your truck is your life, and don't want to add yet another maintenance item to your burgeoning list (like annual rad flushes and BS like that), I haven't found the perfect (=cheap, permanent) solution. They do sell replacement generic wiper arms at auto stores (I've tried that-- works for a couple years). You can try heat and lots of lube (works for a couple months, probably depends on extent of corrosion). You can try drilling out the pin and finding some type of replacement: I haven't found a good one yet, at that point I went to aftermarket arm. Bending the arm is a temporary, 'treat-the-symptom' solution: eventually the pin will freeze up, and no amount of arm-bending will result in contact through the entire range.
Happy holidays,
Kenton