FMC920 + EYE Beacon: false Lost events (AVL 10831) while beacon is nearby

Telematics Issue
1

Hello,

I am experiencing repeated false “Lost” events when using a Teltonika FMC920 with a Teltonika EYE Beacon (BTSID1).

Device:
FMC920
Firmware: 04.00.00 Rev.14
Configuration: 12.0.0.0
EYE Beacon: BTSID1
EYE mode: Lost & Found
Identifier: ID

Problem:
The FMC920 generates AVL event 10831 (Lost EYE Beacon) even when the EYE Beacon is physically next to the FMC920.

The problem is especially reproducible when the FMC920 wakes up or detects movement. The beacon remains next to the tracker and is not moved away.

I confirmed in the raw AVL data that the FMC920 itself generates these events, so they are not generated by the monitoring platform.

Examples:

  • Found: AVL 10829
  • Lost: AVL 10831
  • False Lost events have occurred with very strong RSSI, including approximately -28 to -31 dBm.

I have also observed alternating events such as:
10829 Found → 10831 Lost → 10829 Found → 10831 Lost
while the beacon remains next to the FMC920.

Tests already performed:

  • Non Stop Scan enabled/disabled
  • BLE Scan Duration changed
  • Scan retries tested with different values
  • EYE Beacon Clear Timeout tested with 5, 15 and 30 seconds
  • EYE List Search RSSI threshold changed from -60 to -90 dBm
  • Data Clear Period changed from 10 to 60 seconds
  • Tested with external power and FMC920 internal battery
  • Standard Beacon Detection disabled while EYE Lost & Found remained enabled

None of these tests eliminated the false Lost events.

Could you please clarify what exactly causes the FMC920 firmware to generate AVL 10831 in EYE Lost & Found mode, and whether this behavior is a known issue with FMC920 firmware 04.00.00 Rev.14?

I can provide FMC920 configuration and debug logs if required.

Thank you.

2

Hi,

Thanks for writing to us.

Please note that the Lost and Found events are completely dependent on the BLE scanning/search process. When the device scans for a beacon and detects it, the beacon is reported as Found. During a subsequent scan, if the beacon is not detected due to changes in the RSSI level or other BLE conditions, it may be reported as Lost.

To improve the stability of these events, I suggest disabling Non-Stop Scan and using the recommended settings under the Beacon tab.

Additionally, please check the RSSI Threshold/Averaging Timeout settings under the Beacon List. This parameter defines how quickly the current RSSI value changes toward the newly detected RSSI value.

For example, if the current EYE Beacon RSSI is -40 dBm and the FMB detects the same beacon at -60 dBm, with the Averaging Timeout configured to 10 seconds, the RSSI value will gradually change from -40 dBm to -60 dBm over 10 seconds.

This setting can help prevent sudden RSSI fluctuations from causing unnecessary Lost/Found events.

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Screenshot_2026-09-24-19-53-01-18_24f46b13821d929ef541d5f56b6d7b31
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Hi,
Thank you for the suggestion. I tested the recommended settings.
Non-Stop Scan is disabled, and I changed RSSI Averaging from 5 to 10. I saved the configuration and rebooted the FMC920.
Unfortunately, the false Lost event still occurs when the EYE Beacon is physically next to the FMC920.
During the latest test, FMC920 generated AVL event 10831 (Lost) while the beacon remained nearby. The event contained RSSI = -51 dBm and state: “lost”.
So increasing RSSI Averaging to 10 did not resolve the issue.
Could you please advise what we should check next?