Cannondaleriders

Rebuilt motor installed in frame and hooked up shifter upon shifting it does not return to center until forced.
Could this be a problem in the shift drum or what am I looking at?
Thanks for any info

Is the motor installed and the gearbox lubed?... Hopefully a shifter pawl tophat is not missing or cracked. Or maybe the shifter inner barplate is bent, or a spring is not correct in the drum ratchet... all requiring a motor drop. Hopefully you get lucky, before having to do that.