hi,
--- do you have the results of a speedtest on the host and on the vm?
--- this has solved slow windows networking speeds with rclone, might help you too.
https://forum.rclone.org/t/rclone-25-50mbps-slow-transfer-speed/29157/2?u=asdffdsa
--- if a linux machine is not handy, might do initial testing on wsl.