Groovy multithreading stops unexpected - multithreading

Question

I try to check if a graph is hamiltonian by generating and checking for random paths on it but the script ends without reaching it's result. I also keep a mutex made of a semaphore for the result and this condition is well preserved until the script returns with null and not reaching the final prints.
def pathFinder(){
def permutation = []
for (int i = 1; i <= noOfNodes; i++)
permutation.push(i)
while(true){
if( mutex.tryAcquire(MAX_TIME,TimeUnit.MILLISECONDS) )
{ println "mutex acquired"
if(finalFound){
//check if another thread solved the problem
mutex.release()
println "mutex released - solution found"
break
}
println "solution not found"
//release the lock while checking the permutation
mutex.release()
println "mutex released for others to start looking"
permutation = permutation.sort { new Random().nextInt() }
println "permutation generated: "+permutation
if(isPathHamiltonian(permutation)){
if(mutex.tryAcquire(MAX_TIME,TimeUnit.MILLISECONDS))
{
println "mutex acquired for result"
finalPermutation = permutation
finalFound = true
mutex.release()
println "mutex for result released"
break}
}
}
}
}
def threads = []
noOfThreads.times(){
def thread = Thread.start {
pathFinder()
}
threads << thread
}
println "I start waiting"
threads*.join(MAX_TIME)
println "I joined the finished"
if(finalFound == true) println "Graph is proven to be hamiltonian : " + finalPermutation
else println "Graph was not found hamiltonian"

Answer 1

the following simplified code works fine:
def noOfThreads = 3
def MAX_TIME = 30000
def threads = []
def pathFinder(id){
def t=System.currentTimeMillis()
println "thread $id start"
Thread.sleep(3000+id*100)
println "thread $id end: ${(System.currentTimeMillis() - t)/1000} sec"
}
println "START"
noOfThreads.times{id->
def thread = Thread.start {
pathFinder(id)
}
threads << thread
}
threads*.join(MAX_TIME)
println "END"
result:
START
thread 0 start
thread 1 start
thread 2 start
thread 0 end: 3.002 sec
thread 1 end: 3.1 sec
thread 2 end: 3.2 sec
END
even if you'll have exception in any thread this code reaches the end.
so, multi-threading works fine and the problem somewhere in the rest of your code.
provide runnable code, so we can see the problem ...