Issue with Sigma 24-70 f/2.8 DG DN II and Sony A7 IV

[ThatDangSydney]

Posted this to Reddit, but figured I could ask here as well. Last week I upgraded from an A7 II to the A7 IV. Today I swapped out my Sony 24-70 f/2.8 GM (the original version) for the Sigma 24-70 f/2.8 DG DN II. After using the new lens this afternoon I realized there was an odd sound when turning on the camera as well as an issue where the camera screen would be on but the shutter won’t release and the camera will not turn off. Any ideas what this could be? I feel like it must be related to the lens since when I put the Sony lens back on I cannot recreate the issue. Anytime the sigma lens is on the issue will happen after a few times of turning the camera off and back on again (updated the firmware from 4.0 to 5.0 and now the issue happens anytime I turn the camera on, causing it to be unusable. No issues when there is no lens attached or the Sony lens is attached). The only way to get the camera to turn off is to remove the battery. Both the camera and lens are on the most recent firmware. Any help or insight would be appreciated!

Should note that the lens was bought new from B&H. 

Here is a link to the Reddit post which includes a video of the issue: 

 

Edited September 20 by ThatDangSydney

[Richard A]

I would be returning the lens…

[ThatDangSydney]

On 9/20/2025 at 9:03 PM, Richard A said:

I would be returning the lens…

Yeah, B&H got back to me today apologizing and offering a refund. Strangely, I dug out my old A7 and tried the lens on there. No issues. Put the lens back on the A7 IV and now it seems to be working as normal. However, at the price point I’d rather just exchange it for a different one in case it happens again. Really love the lens though.

[Richard A]

Any reason you decided to replace the Sony lens with the Sigma one in the first place?