You can ask the websites' people anyway - whether it's Facebook, Google, or whatever.
It'd be useful if other people tell if they experience such problems: you could clarify which exact configuration you have when you do - the browser build and mode (if it's Turbo enabled, blocking extensions, the AV's or other apps' active protection for the browser on, etc.), [other] proxies used, IP type, maybe LAN "filters"? Like that.
Maybe it depends on/triggered by something particular among all that...