Thundercracker is definitely flawed in that his shoulder holes are too big. There are workarounds, but it's basically a defect. Skywarp is a little bit better and the others are perfect. Reports of fragility are false.
I stand by the belief that Hasbro will never release a G1-painted Thundercracker, so unless gaudy G2 is going to satiate you, you need to find another option, and probably quickly if you're price sensitive.