First of, let's look at the problems you've had so far:
Prime First Edition Arcee: One of the arms would not stay on. Returned, but could not exchange due to lack of inventory.
I believe that's a ball-and-socket joint, which can be a miss in some cases if the ball isn't fully formed. It can hit in larger toys, but rarely does.
“Rage over Cybertron” Optimus Prime: After transforming a few times, the front hood piece broke off.
Clear plastic is far more rigid than regular plastics, meaning it doesn't bend as much before snapping. That's why it's hardly ever used for joints or pieces that are under constant stress.
Masterpiece Thudercracker: The toy is fine, but the box and instructions did not reflect significant changes between Thundercracker and Skywarp. Plus, the illustration on the box was for a different Thundercracker toy. It all seemed very careless.
Not to the casual consumer. Hasbro really loves to take the easy and quick route if need be when it comes to packaging illustrations. Anybody remember Energon Rapid Run, Treadbolt and Ultra Magnus? They were repaints, but their packaging showed the original toys instead (Sideways, Scavanger and Overload). Besides, the toys shown are usually handpainted prototypes which are then photoshopped to look shiny. Plus, there's the disclaimer "Product and colors may vary"
Masterpiece Optimus Prime: Parts of the chrome bumper were not painted properly.
Paint can be a hit and miss. Paint plus chrome especially.
Generations Blitzwing: A side piece of the head, and the pin that enabled the three-face piece to turn, were missing. Returned, but could not exchange due to lack of inventory.
Be thankful that was the only problem. Blitzwing has a couple that are extremely common, like the shoulders not pegging in properly, or the face not being able to turn. That is one Hasbro should have looked into by now.
Generations Sandstorm: The front landing gear was in the wrong position, such that I had to pop the head off in order to transform it the first time.
But no problems afterwards? I think I read about that a couple of times.
Beast Hunters Voyager Optimus Prime: The sword got stuck in the right hand, and I was unable to remove it without breaking off the handle.
Anybody else had that? Is it even possible for either the peg to be too thick or the hole to be too small on a single specimen?
Masterpiece Soundwave: On Buzzsaw and Laserbeak, the top fins on the weapons have such tight hinges, and the plastic is so soft and thin, that it’s very difficult to transform them without bending or breaking the fins. I have already broken one, and I have been very careful.
Those two have confirmed wide-spread design flaws with anything that folds out. TakaraTomy and Hasbro should be aware, but they'll fix anything remains to be seen.
To wrap things up, Hasbro's Customer Service is pretty notorious for standardized letters (tl:dr), hardly of help and especially when it comes to exchanges: "product of equal or lower value". So yeah, we don't really have faith in them.
The resident Rewind... well, half of one

- Jelze Bunnycat =:3
Looking for:
- TR Furos (Hardhead's head) and Crashbash (lost him

)
- PotP Punch head
- TR Galvatron right arm (the gun one)
- CW Brake-Neck/UW Wildrider, CW Offroad
- TR Twinferno & Grotusque
- Greenlight, Lancer and PotP Elita-1
- Legacy Core Slug, Sludge & Snarl