ALS tower white needle guide is shuddering and sticking when entering sample and wash vials

Try taking the syringe out and running it and see if it stops. The needle guide is a solid piece that is just pushed down by a spring. Maybe the spring is worn out. Do you have another tower you could try swapping it with? Still I don't know why it is shuddering. Maybe the syringe motor is bad. You can send it in for repair and get a loaner to use.

Try tightening the black knob that holds the sample turret onto the turret motor. The turret is keyed onto the motor and the knob just holds it down, but if it has any wiggle room you might see the shuddering shown in the video.

After that, remove the syringe and then very carefully try pushing the needle guide upwards against the spring. It should move freely up and spring back down. Let us know if it doesn't.