Help See-Through Wall on 3d print

[DavidGrant 0]

I am designing a phone stand and have an issue on the front wall when printed, not sure if it is model related or slicer related.

 

On the back is a channel for the charge cable, but when printed you can see the channel outline through the front wall. 

 

Using Cura 4.9.1 - Ender 5 Pro

 

The thickness of this part of the model is 1mm - It's like it is not adding infill but top/bottom, which makes me think it's the model that has an issue.

 

The rear 1mm wall is the same but seems to be fine when printed. Overall model thickness is 7mm and walls shown need to stay the same so the third party part fits.

 

Image attached - Any advice would be very helpful please.

 

Thanks

Dave