Dear Vern Thank you for contacting FOBO No, You don't need to release sensors when your are upgrading sensor's Firmware, Please only follow the App instructions to upgrade sensor's Firmware, Should you have any issue arise, you may revert to us for further assistance by writing an email to "cx@my-fobo.com", Best Regards Amir Bayati Customer Experience | Salutica Allied Solutions Sdn. Bhd. (a subsidiary of Salutica Berhad) 3 Jalan Zarib 6, Kawasan Perindustrian Zarib, 31500 Lahat, Ipoh, Perak, Malaysia M +6016 787 3175 | my-fobo.salutica.com.my