Phone Apps BLF Light On Wrong Button

Rest Phone Apps - 14.0.1
Endpoint Manager - 14.0.23

We are using the DND Rest Phone Apps button with Yealink SIP-T29G phones. We had it assigned to line button 7 via Endpoint Manager and it was showing the light on the correct button. We eventually decided to move it to line button 6 and made the applicable changes in the template in endpoint manager. The line label moved correctly to position 6, and pressing the button next to it toggles DND. However, button 7 still shows the associated light (red when DND is on, and no color when DND is off).

We've tried resaving and rebuilding configs multiple times, rebooted phones, deleted and readded extensions in Endpoint Manager - nothing has helped. Checking in the phone's web interface, there is no entry at all for Line Key 7 - everything looks perfect in Line key 6.