Ugh...just so everyone knows, there is ANOTHER part of Optimus in this set to watch, it has a miniature version of Trypticon's issues. The hip forwards/backwards ratchet springs (ACTUAL METAL SPRINGS!) are so strong they can damage the ratchet teeth or even force the plastic apart, breaking the screw holes. I had noticed the tightness and opened it to give it some cube lube, then saw the much worse report in TFW, so I reopened it and saw that despite the lube I was getting some tooth chips, so I just removed the two tiny springs and plastic ratchet teeth, and put them in the box to save. The hips are so big they work as giant smooth swivels without falling over, and he does have multiple figure stand options anyway. The hips don't actually have to even move for any of the modes, either, but I figure better to be able to reassemble it properly later than have to glue it together as best I can. The springs despite being very small are so strong I have trouble squeezing them with my fingers.
Edit: the part you open to get to the springs us the lower pelvis area itself, unscrew all of the ones on the silver waist area with him face down, it'll push itself apart. The springs are on the back plate and will probably fall right out. Save those for future reuse, then just screw the waist back together and you have a less self-supporting but less self-breaking Prime, and that first part can be fixed with the stands.
Ugh...springs...why, I hope I never see another spring aga-wait, I think I already made that wish, except it Coily is a lazy bum and only applied it to the torso where it would have actually HELPED...