If you are migrating a site larger than 100GB (e.g., 250GB), the web UI is useless. Use WP-CLI.
A 100GB file requires substantial server memory to unpack. If it freezes, your server is running out of RAM. Contact your host to temporarily boost your memory_limit to 4G or 8G , or switch to a command-line restoration tool if you are on a VPS. "Site Size Exceeds Allowed Limit" Pop-up allinone wp migration 100gb fix