Right at the start of the test it fails:

Opening core file, please wait...
hsdb> hsdb> + verbose true
hsdb> + jstack -v
Deadlock Detection:

No deadlocks found.

"hsdb> + quit
sun.jvm.hotspot.debugger.UnalignedAddressException: 8baadbabe
at jdk.hotspot.agent/sun.jvm.hotspot.debugger.windbg.WindbgDebuggerLocal$1.checkAlignment(WindbgDebuggerLocal.java:106)
at jdk.hotspot.agent/sun.jvm.hotspot.debugger.DebuggerBase.readCInteger(DebuggerBase.java:357)
at jdk.hotspot.agent/sun.jvm.hotspot.debugger.DebuggerBase.readAddressValue(DebuggerBase.java:462)
at jdk.hotspot.agent/sun.jvm.hotspot.debugger.windbg.WindbgDebuggerLocal.readAddress(WindbgDebuggerLocal.java:312)
at jdk.hotspot.agent/sun.jvm.hotspot.debugger.windbg.WindbgAddress.getAddressAt(WindbgAddress.java:71)
at jdk.hotspot.agent/sun.jvm.hotspot.types.basic.BasicTypeDataBase.findDynamicTypeForAddress(BasicTypeDataBase.java:238)
at jdk.hotspot.agent/sun.jvm.hotspot.runtime.VirtualBaseConstructor.instantiateWrapperFor(VirtualBaseConstructor.java:104)
at jdk.hotspot.agent/sun.jvm.hotspot.oops.Metadata.instantiateWrapperFor(Metadata.java:77)
at jdk.hotspot.agent/sun.jvm.hotspot.oops.Oop.getKlassForOopHandle(Oop.java:212)
at jdk.hotspot.agent/sun.jvm.hotspot.oops.ObjectHeap.newOop(ObjectHeap.java:181)
at jdk.hotspot.agent/sun.jvm.hotspot.oops.VMOopHandle.resolve(VMOopHandle.java:61)
at jdk.hotspot.agent/sun.jvm.hotspot.runtime.JavaThread.getThreadObj(JavaThread.java:355)
at jdk.hotspot.agent/sun.jvm.hotspot.runtime.JavaThread.getCurrentParkBlocker(JavaThread.java:407)
at jdk.hotspot.agent/sun.jvm.hotspot.runtime.DeadlockDetector.print(DeadlockDetector.java:80)
at jdk.hotspot.agent/sun.jvm.hotspot.runtime.DeadlockDetector.print(DeadlockDetector.java:39)
at jdk.hotspot.agent/sun.jvm.hotspot.tools.StackTrace.run(StackTrace.java:62)
at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor$27.doit(CommandProcessor.java:1153)
at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor.executeCommand(CommandProcessor.java:2212)
at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor.executeCommand(CommandProcessor.java:2182)
at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor.run(CommandProcessor.java:2053)
at jdk.hotspot.agent/sun.jvm.hotspot.CLHSDB.run(CLHSDB.java:112)
at jdk.hotspot.agent/sun.jvm.hotspot.CLHSDB.main(CLHSDB.java:44)
at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.runCLHSDB(SALauncher.java:281)
at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.main(SALauncher.java:500)

This just started the past day. 5 failures already. The test task JVM args are:

-XX:+CreateCoredumpOnCrash -XX:+UseZGC

Virtual threads are not involved (no vthread wrapper).

Note the following two frames and the stack trace above them:

at jdk.hotspot.agent/sun.jvm.hotspot.oops.Oop.getKlassForOopHandle(Oop.java:212)
at jdk.hotspot.agent/sun.jvm.hotspot.oops.ObjectHeap.newOop(ObjectHeap.java:181)

This is the same as what we are seeing with JDK-8283578. However, JDK-8283578 is been going on for a while now, where as this issue just started in the past day. Also, JDK-8283578 is with -Xcomp test tasks, not ZGC.