0STERIZER 4094 MOTOR WORKS AND SHAFT SPINS BUT THE BLADES SPIN SLOWLY OR NOT AT ALL AND IT MAKES A LOUD SQUEALING SOUND.

Either the coupling from the motor with the fingers on it is not really attached to the motor shaft or the drive on the blade that engages with it is not attached to the blade shaft. One other thing is that on some models if the rubber jar seal between the beaker and the blade carrier is in the wrong place it can raise the blade drive to not engaging properly with the motor coupling. The gasket goes between the jar and the blade carrier, not under the blade carrier.

I don't have one, but inspect the shaft, it looks like there is a key on the shaft, then inspect the inside of the blade where it goes on top of the shaft, see if it looks like the shaft has spun out the blade and this is why it's not spinning.

Remove the blade and the container, then turn on and see if the shaft is spinning, it should be most are a direct drive.

So now if the shaft is spinning, that most likely means that the blade hole is broke where it sets on top of the shaft.

Look closely at the inside of the blade, you should see some type of damage like the groves are worn, I hate to see you buy one and it was the shaft that wore, but usually the blade will go first.

make sure blade is pressed tightly onto shaft... should click into indent. if not then you need a new blade piece.- stripped

As stated earlier it could be the shaft needs lubing, remove the bottom part of the blender blade... the rubber thing that engages on the motor. I started with WD-40 and worked some lithium grease into it. Spins like new now.

The shaft has probably siezed at the bottom near the blade. The seal can fail and let liquid inside the shaft and gunge it up.
Take the orange handle apart, then unscrew the four steel pins, then pull out the motor. From the blade end, take the screw from the blade and prize it off. Then pull the shaft out from the top and clean it. It may be stuck - push a blunt nail or similar in the bottom to free it. Clean the shaft and solidified debris inside the tube. Then reassemble carefully.

Sounds like the teeth are stripped underneath the blade. Make sure it's put together correctly before you do anything else.
Download Cuisinart CBT 500 Manual

Check the blade with it off the base and make sure that it spins freely. Check the spindle on the base and see if it feels hard to turn. If the spindle turns too easy , then the connection inside the base is broken and needs replacing.

Check and make sure that the shaft in the base housing spins. If it does, the blade assembly has become disconnected from it's shaft probably due to an improper spot weld or peening of the blades to the shaft, or has torn loose or ripped the splines out due to an immovable object trying to be spun. A jammed ice cube can do this. Blade assemblies can be had usually directly through the manufacturer and usually on line. If this has helped, please rate it accordingly.

well it looks to me there is some thing not tight enough connection to ur blade.....as u say it works when empty but when u put soemting in its stops....this means ur blade is not tight on the shaft to the motor......or u may have done something wrong when u had the blender open........recheck ur work and make sure its tight,,,,,
if so u will have ur ice cold drink....cheers i hope so for ur shake

dynamic mx91, motor runs but blade doesn't spin, how do i disassemble the blade & shaft?