Gateway Discovey ping error

After Update Loraserver and Lora-app-server at last version (2.6.0) during ping of Gateway Dicovery
the process failed and the log of loraserver show the error?? Help me!!! I have 3 gateway and same day ago Gateway Disscovery worked correctly.

time=“2019-03-22T10:09:17+01:00” level=info msg=“gateway/mqtt: publishing downlink frame” qos=2 topic=gateway/001bc506702009a9/tx
time=“2019-03-22T10:09:17+01:00” level=info msg=“finished unary call with code OK” grpc.code=OK grpc.method=SendProprietaryPayload grpc.service=ns.NetworkServerService grpc.start_time=“2019-03-22T10:09:17+01:00” grpc.time_ms=0.898 peer.address=“51.75.68.135:55332” span.kind=server system=grpc
time=“2019-03-22T10:09:19+01:00” level=info msg=“gateway/mqtt: uplink frame received”
time=“2019-03-22T10:09:20+01:00” level=info msg=“finished client unary call” grpc.code=OK grpc.method=HandleProprietaryUplink grpc.service=as.ApplicationServerService grpc.time_ms=9.325 span.kind=client system=grpc
time=“2019-03-22T10:09:20+01:00” level=info msg=“backend/gateway: downlink tx acknowledgement received” gateway_id=001bc506702009a9
time=“2019-03-22T10:09:20+01:00” level=info msg=“gateway/mqtt: uplink frame received”
time=“2019-03-22T10:09:20+01:00” level=info msg=“gateway/mqtt: uplink frame received”
time=“2019-03-22T10:09:20+01:00” level=error msg=“finished client unary call” error=“rpc error: code = Internal desc = handle received ping error: get ping lookup error: get ping lookup error: redigo: nil returned” grpc.code=Internal grpc.method=HandleProprietaryUplink grpc.service=as.ApplicationServerService grpc.time_ms=0.981 span.kind=client system=grpc
time=“2019-03-22T10:09:20+01:00” level=error msg=“handle proprietary up error” error=“rpc error: code = Internal desc = handle received ping error: get ping lookup error: get ping lookup error: redigo: nil returned”

There is already an open issue for this: https://github.com/brocaar/loraserver/issues/385.