I've experienced interruptions mid-clone (with no apparent way to resume them) when trying to clone repos on unreliable connections, and perhaps a similar issue is happening with connections between continents.
The only reliable route I’ve found is to use SSH clone. HTTPS is lousy and as you mention, is not resumable. Works fine in Antarctica even over our slower satellite. Doesn’t help if you actually drop, but you can clone to a remote and then rsync everything over time.