Sometimes they lose momentum and just need more insulin. Check out Gracie's SS. I'm dealing with the same thing right now. I thought she was done bouncing....uhh...not yet!
Also....Trixie,Leo, and Rusty had the same issues. SOmetimes they just have to go up to come down.
Hopefully, Thumper will only need a few cycles of more insulin and maybe that will be enough to kickstart her and let her come back down. Good luck!!!!