Jenkins only executes first line of groovy closure - jenkins

Question

I have the following two Classes which work just fine locally in groovy, but once I use them with Jenkins Shared Libraries I run into some issues.
./Template.groovy
class Template {
String arch
String type
def body = {}
Template(type, arch, body) {
this.arch = arch
this.type = type
this.body = body
}
}
./TemplateBook.groovy
import Template
class TemplateBook {
def templates = []
TemplateBook() {
def template = new Template("test", "lnx", { args -> sh('echo "Hello World!"'); sh("echo Test"); sh("echo $args")})
templates.push(template)
}
def getTemplate(type, arch) {
def template
for (def i = 0; i < templates.size(); i++) {
if (templates[i].arch == arch && templates[i].type == type) {
template = templates[i].getBody()
i = templates.size()
}
}
return template
}
}
Using the Template.body directly works just fine (locally and on Jenkins), but using the TemplateBook.getTemplate() only executes the first line of the closure (body).
def templateBook = new TemplateBook()
def body = templateBook.getTemplate("test", "lnx")
body.resolveStrategy = Closure.DELEGATE_FIRST
body.delegate = this
body("test")
Output:
Hello World!
def template = new Template("type", "arch", { args -> sh('echo "Hello World!"'); sh("echo Test"); sh("echo $args")})
def body2 = template.body
body2.resolveStrategy = Closure.DELEGATE_FIRST
body2.delegate = this
body2("test")
Output:
Hello World!
Test
test