The UAS, a DJI Phantom 4 RTK, was being operated in an automated flight mode to survey a railway track and surrounding infrastructure when one of the four propellers detached whilst in-flight. The aircraft rapidly descended from a height of 70 m (230 ft) where it struck the ground in the rear garden of a house. No one was injured.

With the increasing use of UAS for survey work I suppose it was inevitable that some kind of incident would occur eventually.

https://www.gov.uk/government/news/aaib-report-dji-phantom-4-rtk-uas-lost-power-and-dropped-to-the-ground-newtongrange-midlothian

From the report it did so more than "rapidly", as the motors were continuing under normal power even though the drone was upside down. The gem is located on page 5 of the report (https://assets.publishing.service.gov.uk/media/609cf2d98fa8f56a39f36210/DJI_Phantom_4_RTK_UAS_reg_N-A_06-21.pdf).

"The data indicated that, from a height of about 60 m, the aircraft descent rate increased beyond that associated with free fall. This was because of thrust from the propellers whilst the aircraft was inverted."

I guess there might be a software patch for that one in the future, granted though a broken propeller isn't an expected scenario. LOL.

Andrew