We are investigating intermittent loading failures affecting our websites on several iPhones running iOS 26 or later. The same sites open on our tested Android devices, desktop computers, and iPhones running earlier versions of iOS.
In one case, Safari kept loading indefinitely over a Tele2 mobile connection with VPN disabled. On a second iPhone running iOS 26 or later, one of the applications also failed to load; we do not yet know the carrier or whether the website was tested separately in Safari.
The same affected iPhones also cannot load our VK Mini Apps, which are hosted on the same servers as the websites.
For one of the sites, we partially improved the situation by routing traffic through a proxy hosted with a different provider. On the same affected iPhones, the site then opened over Wi-Fi, but it still did not load over mobile data.
During an earlier investigation of a similar failure, server-side packet captures showed incomplete TCP/TLS exchanges: some data did not arrive, or a server response was not acknowledged. That capture covered TCP only, so it did not rule out QUIC attempts or interactions between QUIC and TCP. We have not established where the packets were lost or whether all incidents share the same cause.
We also observed intermittent, selective access failures to the same servers from a desktop using certain VPN connections, while unrelated sites remained accessible. It is not known whether this is connected to the iPhone issue.
Has anyone seen similar behavior on iOS 26 or later over mobile networks? What client-side and server-side diagnostics would you recommend to distinguish routing, MTU, TCP/TLS, DNS, and HTTP/3 issues when the page does not load far enough to run application code?
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