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Make sure you have enough disk space for both your backup archive and the extracted files. Running out of disk space could cause this kind of problem.

Do you have enough memory for all sites running on the server? Generally speaking, you need to ensure the I/O limits for the server are not exceeded when extracting the backup archive. Do keep in mind that extracting a backup archive is very intensive on disk I/O and memory. Some servers may limit the disk I/O or memory you can use in a specific time period. One alternative is to use a different host. Another is to extract the archive on a local server, then upload everything by SFTP (which takes several hours instead of the few minutes it takes for a backup archive to extract).

The same goes for CPU usage limits. Some hosts may have a very restrictive CPU usage limit (what you see with ulimit -t). If it's under 10 seconds you may have to modify the timing settings in Kickstart to make more requests, each one taking a lot less time so as not to hit the CPU usage limit.

Did your device go to sleep? If your device goes to sleep, the browser stops listening to network traffic. This means it will never know when the last extraction step prior to going to sleep finished. When the device wakes up, it will simply receive a network request failure without any further information which triggers a generic error without any content. Try keeping your device from going to sleep while the extraction is in progress.

A lot of modern browsers have a feature which puts "inactive" tabs to "sleep". It usually kicks in after as little as 5 minutes (Firefox), or as long as two hours (Edge). If a tab is in the background, i.e. not the active tab, and/or the browser is no longer in the foreground it will stop JavaScript timers and listening to network requests. Essentially, it works the same as putting your device to sleep, causing the same problems. Keep the extraction as the foreground tab, and keep the browser as the foreground application throughout the extraction process.

Finally, if your server is running at capacity it might start randomly terminating processes. This will cause the extraction to fail without a sensible error message. If this is the case, you need to contact your host to transfer your site to a less busy server.