DigitalOcean OLS Wordpress 503 error during all-in-one WP migration import

While importing my wordpress website's backup as a file (size: 9,39 GB) using the plugin All-in-one WP Migration, the import operation gets stuck at around 50% but it is not deterministic and depends on my upload speed. When I check the console on the browser, it is apparent that this is caused by a 503 error. I tried a lot of things including (i) increasing php constaints (e.g., post_max_size, upload_max_filesize), (ii) increasing request body size and soft/hard limits from the OLS admin panel, (iii) disabling opcode cache, and (iv) checking error logs. The logs do not provide a handful information except from the "oops 503 error"-like message.

The most interesting fact is that I don't face the issue when I have a faster upload speed (tested with a friend of mine and the import was successful).
I doubt this can be a timeout issue but I'm not sure how can I fix this.

Any help is appreciated!


That is way too long, for 9GB, I'd expect the import will be done in a much much short time. Then I am not sure, it could be more possible reasons. Maybe you can find a place that has a faster network as a workaround method.
Yes it's taking a long time with 3mbps upload speed. I don't have any issues with a faster upload speed (10 mbps) and that's the only workaround that I have for now.