Protobuf version should be in sync with gRPC, downgrade to 3.5.1
<log4j2.version>2.11.1</log4j2.version>
<jcommander.version>1.72</jcommander.version>
<!-- should be in sync with protobuf grpc dependencies -->
- <protobuf.version>3.6.0</protobuf.version>
+ <protobuf.version>3.5.1</protobuf.version>
<!-- osgi dependencies -->
<karaf.version>4.2.0</karaf.version>
