Jenkins throws missing method exception when one job calls another job

I'm running Jenkins 2.277.1, and trying to get one job to call another.

The main job (written using DSL), creates a list of identifiers (in this case, of clusters we want to shut down). It then tries to call a "shutdown a cluster" job for each of those clusters.

The call to start the jobs is in groovy. The "ssm_list" variable contains a list of items, with the cluster name and manifest name separated by an underscore (this was inherited code!). The bare bones of the script are as follows. I've tried changing the parameter types so that they match the ones in the job being called (e.g. the "listGitBranches"), or generic (e.g.. "string"), but no combinations seem to work. I've also tried wrapping the call in "wrap([$class: 'BuildUser']) {", and wrapping the job in parentheses ("build(job:...)". The "cluster-shutdown-branch" job is in the same directory on the Jenkins server as the calling one. The job has many more parameters than I am providing, but the rest all have useful default values.  I have the "Pipeline: Build Step" plugin v2.15 installed. 

        stage ('Run shutdown job based on the list'){
            agent none
            steps {
                script {
                    ssm_list.each {
                        def split_vars = it.split('_')
                        echo "Shutting down ${split_vars[0]}"
                            build job: 'cluster-shutdown-branch', parameters: [string(name: 'CLUSTER_NAME', value: split_vars[0], listGitBranches(name: 'MANIFEST_BRANCH', value: split_vars[1])
                    }
                }
            }
        }

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The error I get starts:

hudson.remoting.ProxyException: groovy.lang.MissingMethodException: No signature of method: build.call() is applicable for argument types: (java.util.LinkedHashMap) values: [[job:cluster-shutdown-cmp-branch, parameters:[@string(name=CLUSTER_NAME,value=din-6453h), ...], ...]]
Possible solutions: wait(), any(), wait(long), main([Ljava.lang.String;), any(groovy.lang.Closure), each(groovy.lang.Closure)
   at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:58)
   at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:64)
   at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:54)
   at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
   at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
   at org.kohsuke.groovy.sandbox.impl.Checker$1.call(Checker.java:163)
   at org.kohsuke.groovy.sandbox.GroovyInterceptor.onMethodCall(GroovyInterceptor.java:23)
   at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onMethodCall(SandboxInterceptor.java:158)
   at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onMethodCall(SandboxInterceptor.java:143)

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Any suggestions of where I should look for the problem?