The main contenders I've seen are gRPC and Cap'n'Proto.
I vastly prefer gRPC (Cap'n'Proto's documentation leaves a lot to be desired so it's difficult to use, gRPC comes with threading built in, Capnp does not) and aside from some performance issues, have had zero problems with it.
What kinds of objects are you having issues with? I suspect the problem isn't gRPC/protobuf so much as the code you're using to interact with it. How exactly are you using it?
I vastly prefer gRPC (Cap'n'Proto's documentation leaves a lot to be desired so it's difficult to use, gRPC comes with threading built in, Capnp does not) and aside from some performance issues, have had zero problems with it.
What kinds of objects are you having issues with? I suspect the problem isn't gRPC/protobuf so much as the code you're using to interact with it. How exactly are you using it?