Sigma 17-70 suddenly has twitching issues

I have a Sigma 17-70 F2.8-4 OS HSM and it is awesome.. never had problems.
My friend has one as well, using it with a T4i.

This is what he described:

- Was working great for the 2 years he owned it
- Suddenly there was problems with it out of no where, it was never dropped etc.
- Whether the camera was on manual or auto mode, there is usually a constant vibration sound coming within the lens
- The result is it twitches, when holding it steadily taking pictures or recording a video, it has these twitching vibrations causing shake resulting in shaky video or photos.

I checked it out myself and what I noticed it the lens has this slight vibration sound coming from the inside, not constant but almost all the time. I only changed between auto and manual focus, maybe it could be something to do with the image stabilization feature, or something inside the lens became loose ?

Anyone know what could a common problem and is it repairable

Sounds like the IS is malfunctioning to me. Is he the original owner, and have the receipt? Sigma has good warranty coverage.

5280Pics wrote in post #15925937
Sounds like the IS is malfunctioning to me. Is he the original owner, and have the receipt? Sigma has good warranty coverage.

Exactly what it sounds like to me as well.

What happens if they turn OS off (I'm assuming it has a OS toggle switch)?