On 19 February 2024, a relatively experienced UAV pilot lost control of a ST Engineering Aerospace DrN-355LS whilst operating it on a BVLOS flight about one mile over water from their Sentosa Island location. A brief interruption in receipt of the GNSS position signal by the UAV required the pilot to take control manually but when their attempt to do so did not follow the correct procedure within the allowed 5 seconds, control was lost and the UAV ditched and sank and was not recovered. Improvements to pilot access to and training for reversion to manual control were recommended.