What a Drone Firmware Update Stuck at 40 Percent Usually Means
A drone firmware update stuck at 40 percent usually signals that the aircraft, remote controller, battery, app, or connection path has stopped communicating cleanly during the flashing process.
In many cases, the update is not truly frozen; it may be verifying files, restarting components, or waiting on a weak link in the update chain.
This issue is common across consumer drones from brands such as DJI, Autel Robotics, and similar app-managed systems, where firmware must pass through multiple devices before installation completes.
Understanding where the process breaks helps you fix it without risking corrupted firmware.
Why Firmware Updates Stall at 40 Percent
The 40 percent mark is not universal, but it often appears during a stage where the aircraft is writing core system files or validating data.
If anything interrupts that stage, the update can appear frozen even when the device is still processing in the background.
- Weak battery level: The drone, controller, or mobile device may stop the update if power is insufficient.
- Unstable connection: Wi-Fi, USB, or remote-controller links can drop during file transfer.
- App interruption: Background app switching, notifications, or phone sleep settings can interfere.
- Corrupted firmware package: A damaged download can cause the installer to fail at the same point repeatedly.
- Insufficient storage: Low space on the phone or controller can prevent the firmware file from unpacking properly.
- Hardware mismatch: Firmware for the drone, controller, and battery may need to be updated in a specific order.
First Checks Before You Restart the Update
Before force-closing anything, confirm whether the update is actually stalled or simply slow.
Some firmware packages take longer than expected depending on signal quality, battery state, and the number of connected components.
Check power levels
Make sure the drone battery, remote controller, and phone or tablet are all well charged.
For safety, keep each device above 50 percent, and ideally connect the mobile device to external power if the update is lengthy.
Wait a reasonable amount of time
If the update has been at 40 percent for only a few minutes, it may still be working.
For larger firmware packages, wait 10 to 20 minutes before assuming it is frozen, especially if the app shows ongoing activity.
Look for signs of life
Listen for beeps, watch for LED patterns, and check whether the app shows transfer activity or progress changes.
These indicators help distinguish a delayed update from a failed one.
How to Fix a Drone Firmware Update Stuck at 40 Percent
If the update remains stuck, use a careful, step-by-step approach.
The goal is to restore a clean update path without interrupting the aircraft mid-write.
1. Keep the drone and controller powered
Do not power off immediately unless the manufacturer says the process is unsafe to continue.
If the update is incomplete, shutting down at the wrong moment can make recovery more difficult.
2. Close unnecessary apps and background tasks
On your mobile device, disable battery saver modes, close other apps, and prevent automatic screen sleep.
Firmware utilities often work best when the phone is dedicated to the update.
3. Reconnect using the recommended method
Use the manufacturer’s preferred connection path, such as:
- USB-C or Lightning cable between phone and controller
- Direct app connection over Wi-Fi
- Built-in controller update tool
- Desktop utility or SD-card-based firmware package
Swapping cables, using a different port, or eliminating an adapter can resolve hidden data-transfer faults.
4. Re-download the firmware file
If the package is corrupted, delete the existing download and obtain a fresh copy from the official app or manufacturer site.
Firmware checksums and version files can fail silently when a file is incomplete.
5. Update components in the correct order
Many drones require the aircraft, remote controller, battery, and accessories to be updated separately or in sequence.
Check the official release notes for your model and install updates exactly as recommended.
6. Use a different device
If the mobile app keeps failing, try another phone or tablet with a clean installation of the manufacturer app.
This can rule out device-specific issues such as storage limits, OS restrictions, or app corruption.
Model-Specific Recovery Options
Some drones offer recovery tools when the standard update path fails.
These tools are especially useful if the aircraft partially flashed new firmware but did not finish verification.
- DJI Assistant 2: Desktop software that can refresh or reinstall firmware on supported DJI aircraft and controllers.
- SD card update files: Certain models support offline firmware installation from a formatted card.
- Battery firmware updates: Smart batteries may need separate update cycles before flight is possible.
- Controller firmware refresh: A remote controller may need a matching version before the aircraft update completes.
Always check the latest official documentation for your specific model, because recovery steps vary by product line and firmware generation.
When to Stop and Contact Support
If the drone repeatedly stops at 40 percent after multiple clean attempts, there may be a deeper issue involving the flash memory, controller hardware, or a version compatibility problem.
At that point, manufacturer support can confirm whether the device needs an advanced recovery procedure.
Contact support if you notice any of the following:
- The app reports an error code after every retry
- The aircraft will not reconnect after the failed update
- LEDs flash abnormally or the drone does not boot normally
- Multiple batteries or controllers fail at the same update stage
- The firmware package never progresses beyond the same percentage
How to Prevent Firmware Update Problems in the Future
Most update failures are avoidable with better preparation.
A stable setup reduces the chance of a mid-update interruption and makes future firmware installs much smoother.
- Charge all batteries fully before starting.
- Use official apps, official firmware files, and manufacturer-approved cables.
- Update in a quiet environment with strong power and minimal interference.
- Disable auto-lock, battery optimization, and other device power-saving features.
- Leave enough storage space on your phone, tablet, or controller.
- Read release notes before updating to understand version dependencies.
- Avoid taking off until all components show the same compatible firmware version.
What Not to Do During a Stuck Firmware Update
Some well-intentioned actions can make the problem worse.
Avoid these common mistakes while troubleshooting a drone firmware update stuck at 40 percent.
- Do not power-cycle the aircraft repeatedly without checking manufacturer guidance.
- Do not install random third-party firmware or unofficial repair tools.
- Do not update on a low battery.
- Do not disconnect cables aggressively or during active flashing.
- Do not ignore version compatibility between the drone and controller.
Key Takeaways for Safe Firmware Updates
A stalled update often comes down to power, connection quality, corrupted files, or an incomplete component sequence.
By checking battery levels, re-downloading the package, using the correct update path, and following model-specific recovery tools, most drones can complete the process safely.
If the same percentage appears every time, treat that as a clue rather than a random glitch.
It usually points to a repeatable issue in the update chain that can be fixed with the right order of checks and a clean reinstall.