this kinda worked from windows

scp -i C:\Users\USERNAME\.ssh\id_rsa -rv H:\FOLDER\ USER@IP:/mnt/folder1/folder2

this was a bit better in wsl ubuntu

rsync -avzr -P -e "ssh -i ~/.ssh/id_rsa" /mnt/H/FOLDER USER@IP:/mnt/folder1/folder2

this also continues partial files and is the winner

rsync -vvvr -P --append -e "ssh -i ~/.ssh/id_rsa" /mnt/H/FOLDER USER@IP:/mnt/folder1/folder2