win7 is old and no longer supported but should support sparse files.
maybe the go library has a problem with win7.
--vfs-cache-mode full relies on sparse files
i like that!
full at the price of sparse
let's call that the rclone diet 
let me know, i can do beta testing on that...
if you want, i can setup a win7 vm and do testing.
but keep in mind that it is free to update to from win7 to win10, via micro$oft website...
i have done it over 70 times so far, zero problems.