Reproduce:
1) Apply patch following patch:

# HG changeset patch
# Parent 94bb65cb37d310e64e486a93d9e55ccb1cc2f8c6
8231293: Shenandoah: Traversal fails JVMTI tests

diff -r 94bb65cb37d3 -r 6973ca5f20b3 src/hotspot/share/gc/shenandoah/shenandoahTraversalGC.cpp
--- a/src/hotspot/share/gc/shenandoah/shenandoahTraversalGC.cpp Fri Sep 20 11:07:52 2019 +0100
+++ b/src/hotspot/share/gc/shenandoah/shenandoahTraversalGC.cpp Fri Sep 20 09:02:52 2019 -0400
@@ -696,6 +696,7 @@

   void work(uint worker_id) {
     ShenandoahParallelWorkerSession worker_session(worker_id);
+ ShenandoahEvacOOMScope evac_scope;
     ShenandoahTraversalFixRootsClosure cl;
     ShenandoahForwardedIsAliveClosure is_alive;
     _rp->roots_do<ShenandoahForwardedIsAliveClosure, ShenandoahTraversalFixRootsClosure>(worker_id, &is_alive, &cl);


2) $ CONF=linux-x86_64-server-fastdebug make images run-test TEST=vmTestbase/nsk/jvmti/scenarios/allocation/AP01/ap01t001/ TEST_VM_OPTS="-XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahGCMode=traversal"

(gdb) p *this
$1 = {<CHeapObj<(MemoryType)5>> = {<AllocatedObj> = {_vptr.AllocatedObj = 0x2b515bd2f3d0 <vtable for PLAB+16>}, <No data fields>},
  head = '\361' <repeats 31 times>, <incomplete sequence \361>, _word_sz = 516, _bottom = 0xffe40000, _top = 0xffe400f0, _end = 0xffe41010, _hard_end = 0xffe41020,
  _allocated = 774, _wasted = 66, _undo_wasted = 0, tail = '\361' <repeats 31 times>, <incomplete sequence \361>, static AlignmentReserve = 2}

Region:
| 3806|EU |BTE ffe40000, ffe40000, ffe80000|TAMS ffe40000|U 0B|T 0B|G 0B|S 0B|L 0B|CP 0|SN 0, 0, 0, 0