Node sends data, Gateway Console shows receipt, but is not always transmitted to the application where other GWs listened

A node sends data, these are received by several GWs and displayed in the application. However, a specific GW is not listed even though it also received the data.

As you can see in the pictures, the frame counter is correct.
Where is the problem?
Sometimes (but rarely) the packages go through.

Here ist the paket received from Gateway:
“gw_id”: “eui-323531324e003100”,
“payload”: “QIcrASYA3gkC596Gjp01fR4xaBo7BXow”,
“f_cnt”: 2526,
“lora”: {
“spreading_factor”: 7,
“bandwidth”: 125,
“air_time”: 61696000
“coding_rate”: “4/5”,
“timestamp”: “2020-08-27T05:21:11.414Z”,
“rssi”: -44,
“snr”: 9.5,
“dev_addr”: “26012B87”,
“frequency”: 867300000

Here is the Paket, receive by the Device (without this GW) so why?
“time”: “2020-08-27T05:21:10.838182685Z”,
“frequency”: 867.3,
“modulation”: “LORA”,
“data_rate”: “SF7BW125”,
“coding_rate”: “4/5”,
“gateways”: [
“gtw_id”: “eui-b827ebfffe318abf”,
“timestamp”: 4287944787,
“time”: “2020-08-27T05:21:10.824621Z”,
“channel”: 4,
“rssi”: -108,
“snr”: 6.2,
“latitude”: 49.46956,
“longitude”: 8.48231,
“altitude”: 100
“gtw_id”: “eui-b827ebfffe2c3516”,
“timestamp”: 2293168235,
“time”: “2020-08-27T05:21:10.825243Z”,
“channel”: 4,
“rssi”: -119,
“snr”: -7,
“latitude”: 49.72478,
“longitude”: 8.63597,
“altitude”: 517
“gtw_id”: “eui-b827ebfffe02741b”,
“timestamp”: 1641334403,
“time”: “2020-08-27T05:21:10.821703Z”,
“channel”: 4,
“rssi”: -117,
“snr”: -6
“gtw_id”: “eui-b827ebfffee3b568”,
“timestamp”: 1234841195,
“time”: “2020-08-27T05:21:10.828113Z”,
“channel”: 4,
“rssi”: -113,
“snr”: -3
“gtw_id”: “eui-aa555a00000e3c59”,
“timestamp”: 59240115,
“time”: “2020-08-27T05:21:10.816868Z”,
“channel”: 4,
“rssi”: -100,
“snr”: 9.2,
“latitude”: 49.54429,
“longitude”: 8.58287,
“altitude”: 114
“gtw_id”: “eui-b827ebfffee71696”,
“timestamp”: 92204203,
“time”: “2020-08-27T05:21:10.831429Z”,
“channel”: 4,
“rssi”: -118,
“snr”: -4.8
“gtw_id”: “eui-b827ebfffe4456c3”,
“timestamp”: 1126067867,
“time”: “2020-08-27T05:21:10.855699Z”,
“channel”: 4,
“rssi”: -109,
“snr”: 6.5,
“latitude”: 49.54301,
“longitude”: 8.57017

Ive checked framecounter this is correct on both GW and Device 2526.

The back-end consolidates all incoming packets for a certain amount of time (several hundred milliseconds) before delivering the data to the application. Any packets delivered after that window will be discarded as being a duplicate transmission. Late delivery might be caused by things like a slow (relative) internet connection.

The time window has been chosen to allow the largest amount of gateways to deliver the data, but still allow for the data to reach an end user application which might generate a downlink. As downlinks could be transmitted in RX1, which is 1 second after the node transmitted, a downlink needs to be at the back-end several hundred milliseconds before the 1 second window expires to allow processing and forwarding to a gateway for transmission. All in all a lot has to happen within 1 second.

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Aside: an application really cannot rely on a downlink that is scheduled when handling an uplink to be transmitted as an immediate response to that very uplink. (And if it works now, it may not work at some later time.) See My application's downlink is always queued for next uplink.

This gateway is clearly quite close to the node.

Does that mean they’re both in your lab for testing? If so you may want to see if there’s something going on in terms of network latency.

Or are they both in the field, but happen to be close together?

they are both in the field.
The mast is next to the garden shed