Missing node modules while using deploying using serverless package and deploy command

Are you certain it's a bug?

• Yes, it looks like a bug

Is the issue caused by a plugin?

• It is not a plugin issue

Are you using the latest v3 release?

• Yes, I'm using the latest v3 release

Is there an existing issue for this?

• I have searched existing issues, it hasn't been reported yet

Issue description

We are deploying multiple lambda functions using a single serverless.yml file. Previously, when we inspected the pipeline artifacts, we found that all the required node_modules were installed in each lambda function's zip file. However, in recent pipeline runs, some of the lambda function zip files did not contain all the necessary node_modules.

Serverless version - tried using 3.x version as well 2.x
Node version - 14.15.4

Service configuration (serverless.yml) content

"N/A"

Command name and used flags

serverless package --stage --region --package

Command output

"errorType": "Runtime.ImportModuleError",
    "errorMessage": "Error: Cannot find module 'async'\nRequire stack:\n- /var/task/lambda/tools/index.js

Environment information

2.32.0

Start by reproducing the issue with the reported serverless package command and inspect the generated Lambda zip files, especially the artifact for lambda/tools/index.js. Compare the included node_modules with the runtime error for the missing async module. Done means each packaged function contains its required dependencies and the deployment no longer raises ImportModuleError.