Hello,
I have a very similar problem – Windows 10 1903 client, mac osx mojave 10.14.6 server (remote), NoMachine 6.9.2.
I tried connecting both an usb stick and an iPhone with iOS 12.1.4 (already trusted by windows) – in both cases the device disappears from windows for several seconds (20-30), then appears back.
Unlike luckyBadger though I don’t get any popups on the remote mac – only a mention in the menus that it “failed to connect the device” like in his screenshot.
Any ideas?
Thank a lot!