The following things happen when the 'sourceEncoding' value is misconfigured in your DSL script (AKA assign a value that isn't in the dropdown):

When creating the job, the 'publishers' node is generated empty, no matter if other publishers are also defined.
When regenerating the job, the 'publishers' node is generated properly, but none of the publishers show up in the UI.

Console output of the seed job doesn't complain about anything.

Example:

job("RIP_publishers") {
    publishers {
        cobertura('**/target/site/cobertura/coverage.xml') {
            sourceEncoding('UTF-8') // Invalid
        }
        git {
            pushOnlyIfSuccess()
        }
    }
}