Simple RPC between 2 workers results in `Unknown Event - Canceled @...`

// wrangler.toml
name = "cfw-utils"
main = "src/index.ts"
compatibility_date = "2024-04-04"
compatibility_flags = ["nodejs_compat"]
...

// index.ts
export default class extends WorkerEntrypoint<Env> {
    async fetch() {
        return new Response('Not Authorized', { status: 401 });
    }

    async getThing(thingId: string) {
        this.ctx.passThroughOnException();
        const result = await getThingFromDb(this.env.DB, thingId);
        return new Response(JSON.stringify(result));
    }
}

// wrangler.toml
name = "cfw-utils"
main = "src/index.ts"
compatibility_date = "2024-04-04"
compatibility_flags = ["nodejs_compat"]
...

// index.ts
export default class extends WorkerEntrypoint<Env> {
    async fetch() {
        return new Response('Not Authorized', { status: 401 });
    }

    async getThing(thingId: string) {
        this.ctx.passThroughOnException();
        const result = await getThingFromDb(this.env.DB, thingId);
        return new Response(JSON.stringify(result));
    }
}

// wrangler.toml
services = [
  { binding = "CFW_UTILS", service = "cfw-utils"}
]

// index.ts
export default {
  async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    // ...
    const result = await env.CFW_UTILS.getThing(thingId)
      .then((thing: string) => {
          console.log('(rpc) thing ', thing);
          return thing;
      })
      .catch((err: Error) => {
          console.log('(rpc) error ', err);
          return 'error occurred getting thing.';
      });
    // ...
  }
}

// wrangler.toml
services = [
  { binding = "CFW_UTILS", service = "cfw-utils"}
]

// index.ts
export default {
  async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    // ...
    const result = await env.CFW_UTILS.getThing(thingId)
      .then((thing: string) => {
          console.log('(rpc) thing ', thing);
          return thing;
      })
      .catch((err: Error) => {
          console.log('(rpc) error ', err);
          return 'error occurred getting thing.';
      });
    // ...
  }
}

Unknown Event - Canceled @ 4/5/2024, 5:49:01 PM

Unknown Event - Canceled @ 4/5/2024, 5:49:01 PM