FAQ

Q: Why are we facing M_UNKNOWN error 500 from the Matrix Synapse server?

Error Details

2025-01-11T03:47:38.385306Z ERROR w3registrar::matrix: 178: can't sync duo to Http(
    Api(
        Server(
            ClientApi(
                Error {
                    status_code: 500,
                    body: Standard {
                        kind: Unknown,
                        message: "synapse sync failed with status 400 Bad Request: internal error generating sync response",
                    },
                },
            ),
        ),
    ),
)

Answer

This error can occur if your account has exceeded the usual limit of 20 active Device IDs. When this happens, the server may fail to handle /sync requests due to the overhead of managing too many devices.

How to Check for Too Many Devices

Use the following curl command to list all Device IDs associated with your account:

curl -v "https://matrix.beeper.com/_matrix/client/v3/devices" \
-H "Authorization: Bearer <your_access_token>"

Example response:

{
  "devices": [
    {"device_id": "AEQJNOWHXG", "display_name": "Beeper Desktop (Linux)", "last_seen_ip": "", "last_seen_ts": 1730201177000},
    {"device_id": "BGKCFSZTRN", "display_name": "Beeper Desktop (Linux)", "last_seen_ip": "", "last_seen_ts": 1733668251000},
    {"device_id": "BVKAPCXANW", "display_name": "w3r", "last_seen_ip": "", "last_seen_ts": 1736377586000},
    ...
  ]
}

Solution: Remove Unnecessary Devices

Identify and remove devices that are no longer in use. Focus on devices with:

• A last_seen_ts of 0 or very old timestamps.
• Duplicate or generic display names.

Example Cleanup

To remove specific devices, use the /delete_devices endpoint:

curl -X POST "https://matrix.beeper.com/_matrix/client/v3/delete_devices" \
-H "Authorization: Bearer <your_access_token>" \
-H "Content-Type: application/json" \
-d '{
  "devices": ["FJHQEVOVOD", "KSQHECIAAA", "KZIRBZPAHB"]
}'

If required, include authentication:

curl -X POST "https://matrix.beeper.com/_matrix/client/v3/delete_devices" \
-H "Authorization: Bearer <your_access_token>" \
-H "Content-Type: application/json" \
-d '{
  "devices": ["FJHQEVOVOD", "KSQHECIAAA", "KZIRBZPAHB"],
  "auth": {
    "type": "m.login.password",
    "user": "@w3r:beeper.com",
    "password": "your_password"
  }
}'

Verify Cleanup

After removing devices, verify the remaining devices:

curl -v "https://matrix.beeper.com/_matrix/client/v3/devices" \
-H "Authorization: Bearer <your_access_token>"

Prevent Future Issues

1. Reuse Existing Tokens: Avoid logging into the same account unnecessarily.
2. Logout Unused Sessions: Regularly clean up old sessions.
3. Monitor Active Devices: Periodically review the list of active devices to ensure it stays manageable.

By keeping the number of active Device IDs below the limit, you can avoid these errors and ensure smoother synchronization with the Matrix server.