My pipeline definitions include methods from Groovy script files. They are loaded like so:

lib = load('ci/lib.groovy')

The problem with this is that when I click the "Restart Build" button from BlueOcean on a job that uses this method it fails to load the Groovy scripts, which results in failures like so:
groovy.lang.MissingPropertyException: No such property: lib for class: WorkflowScript
{\{ at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:53)}}
{\{ at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.getProperty(ScriptBytecodeAdapter.java:458)}}
{\{ at org.kohsuke.groovy.sandbox.impl.Checker$6.call(Checker.java:290)}}
{\{ at org.kohsuke.groovy.sandbox.GroovyInterceptor.onGetProperty(GroovyInterceptor.java:68)}}
{\{ at }}

...
The same does not happen when I use the "Replay" button from normal Jenkins UI.