StackOverflowError when many items to fetch?

[ALPSMAC]

Exception in thread "ForkJoinPool-1-worker-4" java.lang.StackOverflowError
	at scala.runtime.BoxesRunTime.equals2(BoxesRunTime.java:135)
	at scala.runtime.BoxesRunTime.equals(BoxesRunTime.java:121)
	at scala.collection.immutable.HashMap$HashMap1.get0(HashMap.scala:200)
	at scala.collection.immutable.HashMap$HashTrieMap.get0(HashMap.scala:327)
	at scala.collection.immutable.HashMap$HashTrieMap.get0(HashMap.scala:327)
	at scala.collection.immutable.HashMap$HashTrieMap.get0(HashMap.scala:322)
	at scala.collection.immutable.HashMap.get(HashMap.scala:53)
	at fetch.InMemoryCache.get(cache.scala:43)
	at fetch.interpreters.ParallelJoinPhase$$anon$2.apply(ParallelJoinPhase.scala:90)
	at fetch.interpreters.ParallelJoinPhase$$anon$2.apply(ParallelJoinPhase.scala:87)
	at cats.free.FreeTopExt$.modify(freeinspect.scala:51)
	at fetch.interpreters.ParallelJoinPhase$$anon$2.apply(ParallelJoinPhase.scala:95)
	at fetch.interpreters.ParallelJoinPhase$$anon$2.apply(ParallelJoinPhase.scala:87)
	at cats.free.FreeTopExt$.modify(freeinspect.scala:51)
	at cats.free.FreeTopExt$.modify(freeinspect.scala:52)
	at fetch.interpreters.ParallelJoinPhase$$anon$2.apply(ParallelJoinPhase.scala:96)
	at fetch.interpreters.ParallelJoinPhase$$anon$2.apply(ParallelJoinPhase.scala:87)
	at cats.free.FreeTopExt$.modify(freeinspect.scala:51)
	at cats.free.FreeTopExt$.modify(freeinspect.scala:52)
        ...

Cache implementation is thus:

  case object PassthroughCache extends fetch.DataSourceCache {
    override def update[A](k: fetch.DataSourceIdentity, v: A): DataSourceCache = this
    override def get[A](k: fetch.DataSourceIdentity): Option[A] = None
  }

Not quite sure what exactly is causing the Stack Overflow here, or if we can do anything about it... Any ideas? Happy to help address the issue if someone can point me in the right direction.

[ALPSMAC]

Thinking that perhaps the cause was due to interpreting to a Future (which I know has stack safety issues), I tried converting over to interpreting into a Monix Task. No luck though. Still getting the same Stack Overflow error.

[ALPSMAC]

Additional Info: I am performing a fetch of 3600 items via a fetchMany operation, batched into groups of 360, with parallel batch execution.

[ALPSMAC]

Okay - I've done some more poking and if I up the JVM stack size I can get the test case to pass. Closing as a limitation, but not an issue.