error on 'fullySpecified' of webpack.config.js - but no config exists - node.js

Question

I get this strange error:
WebpackOptionsValidationError: Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema.
- configuration.module.rules[1].resolve has an unknown property 'fullySpecified'. These properties are valid:
object { alias?, aliasFields?, cachePredicate?, cacheWithContext?, concord?, descriptionFiles?, enforceExtension?, enforceModuleExtension?, extensions?, fileSystem?, ignoreRootsErrors?, mainFields?, mainFiles?, moduleExtensions?, modules?, plugins?, preferAbsolute?, resolver?, roots?, symlinks?, unsafeCache?, useSyncFileSystemCalls? }
when using sls deploy
(to deploy to aws serverless)
however I don't have a webpack.config.js file nor have I ever set a config setting with "fullySpecified" before.
What I have tried:
searching the project for the term: 'fullySpecified' - it does not exist.
no webpack.config.js (as was originally the code)
a webpack.config.js with a basic config:
module.exports = {
target: 'node',
mode: 'production'
};
What I have found:
https://githubmemory.com/repo/AnomalyInnovations/serverless-bundle/issues/259
Context:
The code is 9 months old and worked last time I was working on it
I used npm update
Operating System: linux
Node Version: 14.16.1
Framework Version: 2.61.0 (local)
Plugin Version: 5.4.5
SDK Version: 4.3.0
Components Version: 3.17.1
package.json:
"dependencies": {
"axios": "0.21.1",
"cors": "2.8.4",
"custom-env": "^2.0.1",
"dotenv": "^8.2.0",
"express": "4.16.4",
"stripe": "6.12.1",
"uuid": "3.3.2",
"aws-sdk": "^2.639.0"
},
"devDependencies": {
"babel-core": "^6.25.0",
"babel-loader": "^7.1.1",
"babel-plugin-transform-runtime": "^6.23.0",
"babel-polyfill": "^6.23.0",
"babel-preset-env": "^1.6.0",
"nodemon": "1.18.4",
"serverless-bundle": "^5.0.2",
"serverless-pseudo-parameters": "^2.5.0",
"serverless-webpack": "^5.5.4",
"webpack": "^5.58.0"
}