I'm familiar with this issue. I find spawning in a new model and then copy/paste the animation from the broken model to the new one, fixes it. Just make sure no IK rig is attached when copy and pasting the animations.

It didn't exactly work, but I did fiddle around with it some more until it did. Thanks for the help, appreciate it. Definitely satisfied with the capabilities of your Sonic models, that's for sure.

It happened exactly the same to me, I already had rendered the animation before the update so there is no problem but when I opened the document the model was just broken, the only thing I just wanted to ask you is if you could get back the previous eyes to this model, I really liked the new ones, the new eyes have Sonic Adventure vibes and I love it, but I don´t know if you could put the option of choosing which eyes the user wants to use, I tried with "add materials" "string" and then selecting the Amy Rose´s eyes, it worked but they seem a little bit small on the Sonic model, so yeah that´s my petition, thank you for your attention.