dhhdjbd
Probably an issue with either your profiles (it puts the app to sleep) or the app.
Could try unrestricted battery for both apps and experiment again?
That app doesn't use WiFi or cell data. It can work with airplane mode on, no WiFi.
This means there isn't really a bottle neck for file transfers. 8GB will take time to copy to/from the same SSD but a few min or less.