Part 107 UAS pilot reported experiencing a number of issues with a new UAS which resulted in a fly away and crash into the ground.

Narrative

On Day 0; during a public safety drone demonstration in Location A; I encountered a significant issue with my issued aircraft. The aircraft was experiencing intermittent self-descending behavior. Despite pushing the left stick upward to climb; the drone would unexpectedly; randomly descend. This troubling behavior occurred multiple times during the demo and was witnessed by several attendees. While troubleshooting the issue; I identified the need to update the aircraft to the latest native build and perform a thermal calibration.The following day; Day 1; I performed both the update to the latest aircraft's native software and the thermal calibration. Afterward; I conducted a test flight using the latest firmware; with the aircraft's accessory lighting system (including the DroneTag mount) and the spot light / landing combo. The update appeared to resolve the self-descending problem; and the lighting systems did not negatively affect the drone's performance. However; I noticed the aircraft struggled to come to a complete stop when releasing the sticks; behaving as though in ATTI Mode with horizontal drift. Despite this; the overall flight performance was satisfactory.On the morning of Day 2; I presented the aircraft to members of a fire Department in a static display. They pointed out an issue where the gimbal was stuck off-center. A simple power cycle resolved the problem. During the afternoon of Day 2; I conducted a demo with another group. Before the flight; I calibrated the drone's magnetometer and verified that no further updates or calibrations were necessary. Approximately four to five personnel flew the UKR; with three specifically mentioning the aircraft's difficulty stopping when releasing the sticks; consistent with the earlier ATTI-like (attitude mode) drift. While no other major issues were noted; participants remarked on the difficulty of seeing the screen during outdoor flight; even while using a pop-up tent for shade.Once the demo concluded; I mounted the night time / aircraft lighting accessories to take photos of the accessory setup. With the controller turned on first; followed by the aircraft; I went through my pre-flight checklist without noticing anything abnormal. Standing on the pad; I initiated takeoff. Immediately; due to the sun; I had trouble seeing the screen and could not determine the gimbal's attitude before launch; however I could determine that I had video. As I pressed the launch button; the drone exhibited erratic behavior that can only be described as chaotic.The aircraft shot upward at a rapid pace; appearing uncontrolled; and moved towards nearby pine trees that stood over 75 feet tall. I instinctively pushed the left stick forward to ascend above the tree line; narrowly avoiding the tops by what looked like it was less than a foot. My focus remained on the drone; not the screen; until I relocated under cover to better observe the video feed and telemetry. Although my memory of this phase is hazy; I recall seeing the drone climb to an altitude exceeding 400 feet; though I do not remember pushing the stick past the initial climb to avoid the trees.Attempting to regain control; I pulled the left stick down; bringing the aircraft below 300 feet. I struggled to stabilize the drone for manual landing; finding the stick inputs unexpectedly aggressive and the aircraft's movements exaggerated. I initiated the Return to Home (RTH) function; only to realize that it was set to 'Return to Pilot.' When I left the cover to better visualize the drone; the screen's visibility again became very difficult to see due to bright sunlight. The drone then oriented itself away from the landing zone and started flying off in the opposite direction. Despite my attempts to adjust the RTH through manual input; the drone suddenly descended at a steep angle; almost like a missile; before hitting the ground. I distinctly remember the altimeter displaying zero while I could visualize the aircraft in the air;before the impact.The erratic behavior of the aircraft despite firmware updates; calibrations; and pre-flight checks remains unexplained. The incident highlighted several challenges: maintaining screen visibility during outdoor operations; managing aggressive stick inputs; and ensuring stable flight behavior after updates. Further analysis is essential to understand the root cause of the uncontrolled flight and subsequent crash.Crash report - The aircraft was found on a railroad easement about 500 yards from where the last known location of the aircraft was shown on the aircrafts GCS. The aircraft was found by a demo attendee who failed to take photos of the scene. Aircraft damage included:Broken right rear prop armFront cracked right propVentral - rear of aircraft damage Rear left cracked propMissing D3060 Beacon light I wish that I had been using DroneSense to view the flights replay and better understand what happened to cause the issues experienced with this aircraft. Unclear of what happened to this aircraft leading up to and during it's subsequent crash; the aircraft will be returned to the manufacturer for a DAT file review.