>>6506420>>6506437What I've found is that the hinge on his back can be very slightly too large for the back panel to fit around in jet mode.
Sanding off a bit of paint let the back panel fit properly and made a flush jet mode. You don't need to trim/sand off nearly as much as I did here, I was just seeing what works and when I got to doing it to the other Seeker babies all I needed to do was round off the edges a bit.
The issue is probably just the paint making the hinge slightly too bit to fit where its supposed to, but since I had to do it to Ghost Starscream too it's probably just a matter of really tight tolerances.