Hardware devices, such as a Trezor or Ledger, periodically release firmware upgrades for their devices.
If you have not yet initialized your hardware device and added it to your Casa app and you don't have funds stored with it, you are safe to upgrade your firmware and should upgrade your firmware prior to adding the device to Casa.
Once you've initialized your hardware device and added it to your Casa app as part of your vault setup, we recommend upgrading your firmware with caution, and never more than one device at a time.
Why the caution?
Some firmware updates may wipe the device and require the seed phrase backup to restore. This is not common, but it does happen.
Since our recommendation is that you not keep a copy of your device's seed phrase, if your device is wiped by the update, you may need to perform a recovery transaction using your other keys to swap it in as a new key, because you will not be able to use its previous key if it has been wiped.
If you do have the seed phrase for the device, it is generally safer to update the firmware.
If you do not have the seed phrase for your device, update cautiously, and, to reiterate: only update one device at a time to ensure you still have enough operational keys to move your funds.
It is important, though, to keep the device up-to-date so that it is compatible with third-party software like Electrum or Specter, in the event that you need to perform Sovereign Recovery.