How to debug "Error: Runtime exited with error: exit status 142"

I have a Lambda function written using NodeJS 20 and Typescript. It's too big even with lambda layers so I created a Docker image. It's triggered by a SNS Topic. After trying a bunch of things that didn't work I decided to strip the handler to just three console log statements.

export const handler: SNSHandler = async (event: SNSEvent, context) => {
  console.log("Starting !!!");
  console.log(`Event: ${JSON.stringify(event, null, 2)}`);
  console.log("Stopping !!!");

When I test with even this simple handler I get the following error:

entrypoint requires the handler name to be the first argument
INIT_REPORT Init Duration: 17.69 ms	Phase: init	Status: error	Error Type: Runtime.ExitError
entrypoint requires the handler name to be the first argument
INIT_REPORT Init Duration: 2.31 ms	Phase: invoke	Status: error	Error Type: Runtime.ExitError
START RequestId: 835d7dd3-ce97-4224-9042-faf0b42b34c4 Version: $LATEST
RequestId: 835d7dd3-ce97-4224-9042-faf0b42b34c4 Error: Runtime exited with error: exit status 142
Runtime.ExitError
END RequestId: 835d7dd3-ce97-4224-9042-faf0b42b34c4
REPORT RequestId: 835d7dd3-ce97-4224-9042-faf0b42b34c4	Duration: 4.33 ms	Billed Duration: 5 ms	Memory Size: 1024 MB	Max Memory Used: 3 MB

How do I debug this? I built the Docker image on Bitbucket.

Dockerfile

# --- Build Stage ---
FROM public.ecr.aws/lambda/nodejs:20 AS builder

# Set working directory
WORKDIR /app

# Copy package.json and package-lock.json
COPY package*.json ./

# Install dependencies (using npm ci for clean install)
RUN npm ci

# Copy TypeScript source code
COPY src ./src
COPY tsconfig.json ./

# Install dependancies
RUN npm install

# Build the application (make sure your build script creates the "dist" folder)
RUN npm run build

# Log files AFTER the build in the builder stage
RUN echo "Files AFTER build in builder stage:" && ls -la /app/dist

# --- Final Stage (Lambda Image) ---
FROM public.ecr.aws/lambda/nodejs:20

# Set working directory
WORKDIR /var/task

# Copy package.json and package-lock.json (or npm-shrinkwrap.json)
COPY package*.json ./
COPY --from=builder /app/dist ./

# (Optional, but highly recommended) Set the handler function
ENV AWS_LAMBDA_HANDLER index.handler

# (Optional) Set NODE_OPTIONS for increased stack size if needed
ENV NODE_OPTIONS --max-old-space-size=512