I would have thought that if it was on his screen and in his list, it should appear on mine too!!
Anyone else want to try this with another radarbox user?
I'd be happy to help out if I can, although the results might not be conclusive as my RadarBox range is limited due to aerial position and there are other sharers in the area uploading traffic too.
But I could set up email alerts to you for my local traffic, which you could then use to compare with what you're seeing on the network. While of course that wouldn't prove that everything I was uploading was getting on to the network (since the same aircraft could be coming from other sharers), if you had an alert for something I had on my screen that you couldn't see on the network, then that would point to something wrong.
PM me if you want to try that.