Do you use a VPN? I have a few different ones, and I’ve noticed not all of them work well with private mode. I sometimes get the same messages you’re talking about. I found a guide like this one https://setapp.com/how-to/fix-load-content-error, which goes over different causes and solutions. You might find it helpful too. In my case, the problem was my VPN, and once I figured that out, it stopped happening.