`npm version patch` command failing

I was able to resolve the error by myself. The error was that the patch version was written as 01. i.e. 2018.11.01 instead of 2018.11.1. npm version patch failed without an explanatory message.

Yes, you're correct the semver version number must be a valid integer from [0-9] inclusively.

For reference, npm uses node-semver as their semver parser to deal with versioning on their end. Also, you mentioned the error failed silently, you need to run your command with the verbose flag to see everything.

For example, if you do a npm version patch --verbose, npm would spit out additional information for why the command failed. You can use the verbose flag on any valid npm command

Hopefully that helps!