600D Focus is switching between AF and MF

[Starclassic]

My Sigma 50 mm 1.4 DG HSM Lens is switching bewtween AF and MF when trying to use AF. I've uninstalled ML and Cleared cn funcs and cleared all settings with still no luck. Any Suggestions. Here's a link with video.

[walter_schulz]

Get some cleaning fluid (Isopropyl alcohol, 70 percent or more) and put one or two drops on a microfiber cloth. Clean the len's and cam's contact plates and pins with care.

Causes may be:
Corrosion (treated above)
AF switch
Wobbly EF mount
Len's internal electronics

[Starclassic]

Thanks for the useful advice walter. I tried cleaning the pins and contact plates with no luck. The lens and body are fairly new. I'm assuming it is the AF switch or the internal electronics. Good thing I still have my warranty.