That's where the removable boots come in handy, did you try tugging the material a tad into place after removing the boots and then putting the boots back on . I did, the tightness returned that is one reason I think the boots are removable.
I could be wrong since the instructions say not to remove the boots, but it worked for me and btw the one thing I noticed at least on mine anyway, there is no glue or residue around the boots and knee connection unlike the ASM version.
It seems like my figure was built that way, because both boots snap in snugly with no gaps unlike like I've seen in Clipper's and other videos.
