I ran into an issue with hardware 2FA enabled and a new phone.
One of my Ubikeys is always plugged into my desktop, the other is on my keychain for wireless authentication with my phone.
Apparently, only the most recently used hardware 2FA is allowed to authenticate wirelessly to add a new device. Since my other Ubikey wasn’t wireless the only recourse was to remove the hardware 2FA, add the phone and then re-add the hardware 2FA.
Modern IRUs also take input from multiple sources (GPS, Navaids) to update their drift error. With spoofed GPS, bad drift corrections are made and when the navigation solution eventually fails the IRU is just as unusable.