.lastUpdate stopped working

Setup, Configuration and Use Beginners
1 
var ReentrantLock lock = new ReentrantLock()

rule "Alarm Triggered"
when
  Item Alarms received update 
then
  var boolean gotLock = lock.tryLock() 
  try {
    if(gotLock) {    
      logInfo("Testing", "Alarms received update")
      val alarm = Alarms.members.filter[Contact s|s.lastUpdate("mapdb") != null].sortBy[lastUpdate("mapdb")].last
      if (alarm.state == OPEN) {
        logInfo("Testing", "Test: " + alarm.label)
      }
    }
  }
  catch(Exception e) {
    logError("Alarms:", "Exception in rule 'Alarms': " + e.toString)
  } 
  finally {
    if(gotLock) {
      lock.unlock()
    }
  }
end

This was working, but now I am seeing:

2017-07-07 11:50:39.615 [ERROR] [org.eclipse.smarthome.model.script.Alarms:] - Exception in rule 'Alarms': java.lang.RuntimeException: The name '<XFeatureCallImplCustom>.lastUpdate(<XStringLiteralImpl>)' cannot be resolved to an item or type.

2

break it up and expand code for diagnostics - perhaps group.members is not returning what is expected for example

3

You may find this saga interesting

4

Based on a separate thread this user found some lastUpdate times WAY in the future. Do all the items in your group have reasonable last update times if you print them separately?