We have found that the latest version of the DJI N3 flight controller (version 188.8.131.52) when used with the channel expansion kit (used for our payload release system) can result in the servo becoming unresponsive when trying to activate the payload release.
After testing we believe this is caused by the latest onboard SDK support released with version 184.108.40.206. This issue has been reported to DJI.
We are recommending that HexH2O PRO customers using the payload release system should keep the N3 flight controller on version 220.127.116.11 until DJI have addresses the issue.
You can downgrade the N3 firmware version via the DJI Assistant Software.