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Here's the reason for requiring fixes. Top image shows how the knees are backwards. Looking at the bottom image we see that the fists are upside down. This is how I ended up fixing them. So let's get started.
First order of business is gathering the necessary tools. You'll need a small-headed phillips screwdriver, a hammer, something small to hold against pins that you can tap on (you'll have to look at the pins on the toys to see what would be a good size), pliers, and a surface to hammer on.
For my purposes I used a small 1x16 wire brad to tap on for the pins (after clipping the end off and smoothing it down). For a hammering surface I used a few strips of very soft wood I had laying around that's normally used for levelling furniture, which worked out very well since it was soft enough that the pins could dig right through it when I was tapping (as seen by the holes in the wood). Also in the picture is a small pick, but that's only there because I dropped a couple screws in tight places and used that to fish them out.
We'll take a look at the legs first. Since they are connected to the hip by a ball joint, you can easily disconnect them. Once you get them off, take a look at the inner side of the leg. Using the screwdriver, remove the two screws indicated.
Lift the plastic panel on top from the rest of the leg, making sure not to dislodge the pin holding the foot.
Remove the inner assembly from the leg. The issue here is that the knee assemblies are actually on the wrong legs, so we have to swap them. You'd think at this point you could just swap these two parts, but they won't fit in the other leg due to the way they are designed (the part has a tab that fits into a groove on the leg and only fits one way). So what we have to do is remove the screw indicated by the red circle. You'll have to watch for the part circled in blue. It's got a spring underneath and if you don't hold it down it could pop out on you when you loosen the panel with the screw. They won't all pop out (I only had the first one do it), but keep an eye on them.
Once we've got the panel off, you can see the inside of the part. At this point you'll have 3 screws for each leg, take note that one is shorter than the others (the one you just removed). Looking inside the part we just disassembled, notice how the knee joint piece is tabbed in via a saucer shaped tab. Pull that piece out.
You end up with this. Now you just need to swap the two parts between the legs and rebuild the knee assemblies. It's best to put them inside one of the halves of each leg (line them up with the top edge of the legs) and make sure it looks like the knees are working in the right direction. Finish rebuilding the legs and reattach.
Viola! Skywarp is happy his knees work correctly. Onwards to the hands.
The pin circled in the picture is what you need to remove so that you can fix the hands up.
To make it easier to work on, we'll take his arm off. Tilt it out at the shoulder from his body and you can see a screw there. Loosen it slightly and his arm will come off from the back.
Once you've taken his arm off, it's time to start tapping on the pin. Hold the arm against your hammering surface, brace whatever you're going to hit with the hammer against the arm, and then tap away. You want to work on it from the top of the arm (the side of the arm where his elbow joint would bend at). You can tell you're going in the right direction if the part of the pin that's coming out the otherside is grooved. This is the most tedious part of the whole process. There's probably better ways to do this, but I made do with what I had available.
An image of the pin coming out of the arm with the grooves. Once you get it tapped out a bit, use the pliers to yank them the rest of the way out. I found it easiest to tap the pin until I got past the grooves to the smooth part before using the pliers as the grooves hold it in pretty fiercely.
Once you get the pin out, you'll have this. Now arrange the hands with the arms so that they will be correct after you put them back together.
Time to put them back together. To make it easier on myself on lining up the holes, I put the fist in the arm like this. Put the pin back in the way it came out, inserting it from the bottom of the arm, smooth end first. Use the hammer to gently tap it all of the way in. Then just screw the arms back onto the body.
And there ya go, a seeker who is ready to go cause trouble.
The other seeker issue I had only involved the Thundercracker KO. I don't know how common this particular issue is, but take a close look at the side tail fins that are supposed to fold up when he's in robot mode. Notice how the plastic is fat on the top of the joint area on him compared to KO Starscream to the right. That would be because his fins are upside down and reversed. I hadn't noticed it when I first opened him up and forced it too much, cracking the plastic on his other foot slightly. So now we'll fix this problem.
This involves one pin on each side (to the left has the pin still in place while the right side has the pin removed already). Fortunately, the pins here aren't in nearly as tightly as the arm pins thanks to not having any grooves to bite in. So tap them out so you can get the side fins detached. Now swap them between the feet and align them up so that they are facing the right way with the curved plastic side up (so that they can fold correctly). Lining them up to put the pins back in takes a bit more work here. Best thing I can tell you is look through the pin hole so that you can see out the other side, then line up the fin so that you can still see through. Take the pin and push it into the hole. At least for me the pins were easy to push in most of the way and only required a little tapping to finish them up (which made things easier). That finishes up Thundercracker's foot issue.
Finally, the issue with the Prime molds. Again, the manufacturer put parts on in reverse...and again it is the hands. If we look at the picture we can see that his fingers are actually increasing in size as you go down rather than decreasing. This is a very easy fix though.
Fold down his arm panel and look at the side of his arm. There are two screws here we need to remove, so bust out the Phillips once again.
Remove the panel and you can see the hand on a peg. Slide it off the peg and switch it with the hand on the other arm, lining up the fists so that they look right. You'll know if they're upside down as one side of the hand is fatter than the other and will prevent it from transforming if put on incorrectly. Then just reattach the panels and screw them into place.
There you have it, now you can enjoy your new KO seekers and primes in all their glory (and with parts in the right position too!).