if you take stabilized footage and speed it up, it might end up looking shaky again because you’re exagerating all the bumps ae tried to reduce in the first place. Are you speeding it up whole frames, frame blend, or pixel blend?
I would first make sure that the stabilized footage is locked down 100%. Any perturbations will need to be almost zero.
If it still doesn’t work, either try another method of warp stabilizing or try some other methods.
there’s a free deshaker for virtualdub which might give the desired stabilization. then speed it up in ae or premiere with optical flow.
if all that still doesn’t work, precomp footage, drop the precomp into another layer. timestretch it 50% and apply timewarp 50%. This will average out the shakyness by warping all frames and returning the averaged motion optically.