External HDD keeps turning on while in the rest mode.

You have to select "Turn external Storage off" in power settings when in Always on mode, otherwise it will stay on as the OS checks for updates and game downloads etc.

Ive got a seagate 5TB external HDD

Got it from amazon for £130

Best thing ive brought this year gone are the days of removing old games before installing new ones.

Easy to format all you do is plug it in and your xbox dose the rest for you.

Ive got my xbox on instant on mode and the external HDD turns on and off when i turn the xbox on or off.

Great bit of kit

When the screen goes black, does it immediately happen when you plug the external HDD into the Xbox while it is turned on, or turned off?

Does the Xbox still turn back on normally without the external HDD? What kind of external HDD are you using, by the way?

See here for some troubleshooting steps for a blank screen: http://support.xbox.com/en-US/xbox-one/console/tv-or-monitor-screen-is-blank-while-connected

Allright, seems like we have a similar issue if not the exact same one.

My games dont get the message "installation stopped", but just moves to the "ready to install" pane.

I will try what both of you suggest, to keep the external drive always on, to see if it solves something.

And i agree that i also think something does not work as intended. I would expect that i could use the instant on power mode together with an external hdd, and that the external hdd would act like the XBO's internal. With that i mean that the XBO should
be able to put the external hdd in and out of sleep if it need to use it, when it is turned off in instant on mode.

You can turn off the external HDDs when the console is off by going to settings>power & startup>power & startup mode and stopping the HDD drive staying on when console is off.

If your console is in instant on and set to keep all games and apps up to date this means that the HDD will power up/stay on to download whilst off.