Fix ArduPilot ExternalNav Integration

I’m running an ExternalNav pipeline that takes UWB data through a Raspberry Pi 5, packages it as MAVLink VISION_POSITION_ESTIMATE messages, and feeds it into ArduPilot. Somewhere along that path the position information degrades and the vehicle refuses to accept the estimates. I need your debugging skills to pinpoint the fault and deliver a clean, reliable flow of data all the way to ArduPilot.

You’ll have full access to the C++ firmware on the UWB microcontroller and my current ArduPilot parameters. Mission Planner logs, real-time telemetry, and a reproducible bench test setup are ready to share the moment we start.

Key technologies you’ll be working with include:
• C++ (embedded STM32-class environment)
• Python 3.x on Raspberry Pi 5
• MAVLink 2.0 message packing/parsing
• ArduPilot 4.x EKF / ExternalNav configuration
• Mission Planner for log inspection and parameter tuning
• Decawave-based UWB anchors and tags

Deliverables
1. A concise report explaining the root cause of the failure.
2. Updated code or configuration files that correct the issue.
3. A verification log (or short flight test) showing stable VISION_POSITION_ESTIMATE data accepted by ArduPilot.