I don't know of any, but i'm sure vTiger has it's own file upload section.
They might be best using a download manager app on their computer.
It's a generally accepted fact these days that if you lose your internet connection, you're jaffed, and have to start again.
...And if you've got an unreliable internet connection, you either a) change suppliers, or b) get your own download manager app.
Sorry this isn't the answer you're looking for!
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