@Haytch: Is the issue occurring with all the portrait effects (accessible by tapping the circle in the bottom right of the screen while Portrait Video is selected)? If so, please try tapping on the subject to bring the focus to the foreground, and make sure that it says 'Ready' at the top of the screen before you start recording.
If you're still having problems, head to Settings > Apps > Camera > Force stop > Clear cache, then restart your S24 to see if this helps.
@galaxyfan87: Are you having similar issues with the Portrait Video feature, or is the image blurry when capturing videos in the standard 'Video' mode? If dust has made its way under the glass/into the camera module, then this might explain why the device is having some problems focusing.
To ensure that the dust is not on the exterior, please ensure that the rear camera module of your S24 Ultra is clean, as dirt or foreign objects on the camera lens can interfere with autofocus. I recommend cleaning the lens with a soft, dry, lint-free cloth to avoid scratching or damaging it. Also, if you have a case or cover on the device, make sure that it doesn't cover the edges of the camera lens which can also prevent the camera from focusing.
When you open the Camera app, please try using 'Video' mode, then tap on the viewfinder to bring the subject(s) into focus. For the best results, please make sure that you are in a well-lit area, and you are not too close to the subject.
If the rear camera still won't focus, then please open the Camera app > Tap the cog in the top left > Reset settings > Reset, to see if this helps. Furthermore, head to Settings > Apps > Camera > Force stop > Storage > Clear cache, then restart your device.
