Xbox One S gamepads need disable_ertm set to 1 in order to stay connected after pairing:

https://www.google.com/search?q=xbox+one+disable_ertm

I don't know what this option does or why the gamepad needs it to be disabled. It could be a bug in the gamepad or in BlueZ, I have no idea.

I do know that Xbox One S gamepads are difficult to use on Chrome OS devices due to this issue, since the option can't be changed without entering Dev mode.

Could you look into this issue and figure out what needs to be done to make this gamepad usable for unprivileged users?