protobufjs inconsistent encoding

I'm running into inconsistent behavior when trying to encode my messages. I have the following .proto files.

BaseMessage.proto

syntax = "proto3";
package mypackage;

message BaseMessage {
    string id = 1;
    string event_name = 2;
    string timestamp = 3;
}

CategoryMessage.proto

syntax = "proto3";
package mypackage;

message CategoryMessage { 
    string category_id = 1;
}

syntax = "proto3";
package mypackage;

import "BaseMessage.proto";
import "CategoryMessage.proto";

message EventMessage {
    BaseMessage base = 1;
    CategoryMessage category = 2;
    string action = 3;
    string name = 4;
}

Then my code looks similar to this:

let protobuf = require("protobufjs");

base = {
  id: "test-id",
  event_name: "test-event",
  timestamp: "20221122T123421"
}

category = {
  category_id: "test_category"
}

testEvent = {
  action: "do_something",
  name: "Bob"
}

run(base,category,testEvent);

async function run(base, category, event){
    const rootBase = await protobuf.load("BaseMessage.proto");
    const rootCategory = await protobuf.load("CategoryMessage.proto");
    const rootEvent = await protobuf.load("EventMessage.proto");
    
    const Base = rootBase.lookupType("mypackage.BaseMessage");
    const Category = rootCategory.lookupType("mypackage.CategoryMessage");
    const Event = rootEvent.lookupType("mypackage.EventMessage");
    
    const baseBuffer = Base.encode(base).finish();
    const categoryBuffer = Category.encode(category).finish();
    const eventBuffer = Event.encode(event).finish();
    
    console.log(Base.decode(baseBuffer));
    console.log(Category.decode(categoryBuffer));
    console.log(Event.decode(eventBuffer));
}

The above code will result in the following output:

BaseMessage { id: 'test-id', timestamp: '20221122T123421' }
CategoryMessage {}
EventMessage { action: 'do_something', name: 'Bob' }

For some reason it's missing event_name from base and category_id from category for no reason that I can understand.

Has anyone else encountered this before? Is there a reason certain fields don't seem to work properly? Or am I just missing something obvious?

After more exploration I figured out that protobufjs doesn't support fields with underscores (_), which is unfortunate.