Multisite sub-site images don't show – 403 errors

I have a problem with images showing on my sub-sites. In particular with avatar images.
They show absolutely fine on the parent site – but show missing image question marks on the sub sites and in the console show a 403 error.

I am using Buddypress and have implemented the fix for the upload path of the avatars so I know the path to the image files are correct. Plus – If I copy and paste the image src=”xxxx” into an address bar the image show absolutely fine.

I’m guessing its down to my .htaccess file. I’m on a shared hosting so have no access to the apache settings.

Any help would be much appreciated.