https://www.theregister.co.uk/2018/05/25/cisco_admins_hold_that_ios_xr_update_while_you_get_new_firmware/ > Eight Cisco NCS 6000 line cards need firmware upgrades, after Switchzilla learned they could be bricked by an IOS XR upgrade. > The operating system upgrade in question is IOS XR 5.2.x.