Talon VTOL Conversion Crash

Hi I am in to this building of Xuav Talon to VTOL setup , we had some eventful flights and today we continued our testing, after changing Fixed wing motor from last flight. Takeoff in Qloiter was normal, and we have planned an Autonomous mission with a small grid, but during the transition it felt the transition not happened, and flight was carrying out with Quad motors help, we have initiated a Qrtl as it was little far, the flight took a sharp bank and felt like executed fixed wing flight to reach home, but we able to reach the plane nearby but it started descending and had a hard landing. We are running Arduplane 4.2.2 official, VTOL setup was made on Extended wings for Talon. Just want to know what went wrong , inputs are highly appreciated.