@teamcrw I think the issue is not related the php settings. When the settings are low, it says so in the UI like below:
I am wondering if the issue is max_execution_time per https://lycheeorg.github.io/docs/faq.html#i-cant-upload-large-photos . The default value is set to 200, so that's under 3 minutes (can set it to 0 also to disable). Can you set it to much larger value and try? How long does your upload of 1GB take?
You can also set APP_DEBUG=true in the env file and then restart the app. Check for errors in the browser and also Show Logs in the lychee UI after upload fails.