While debugging JDK-8212159 with slowdebug JVM variant I hit one more crash:

#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (c:\Users\Andrei\java\jdk\src\hotspot\share\runtime/handles.hpp:168), pid=7160, tid=804
# assert(_value != 0LL) failed: resolving NULL _value
#
# JRE version: OpenJDK Runtime Environment (11.0+28) (slowdebug build 11+28)
# Java VM: OpenJDK 64-Bit Server VM (slowdebug 12-internal+0-adhoc.Andrei.jdk, compiled mode, tiered, compressed oops, g1 gc, windows-amd64)
# Core dump will be written. Default location: C:\Users\Andrei\java\jvmti-race\hs_err_pid7160.mdmp
#

Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [jvm.dll+0xf333e1] VMError::report_and_die+0x81 (vmerror.cpp:1269)
V [jvm.dll+0x5c51ae] report_vm_error+0x8e (debug.cpp:232)
V [jvm.dll+0x1f7bc] methodHandle::non_null_obj+0x4c (handles.hpp:168)
V [jvm.dll+0x1e443] methodHandle::operator->+0x13 (handles.hpp:168)
V [jvm.dll+0xad68f8] JvmtiEventMark::to_jmethodID+0x18 (jvmtiexport.cpp:199)
V [jvm.dll+0xad57b0] JvmtiMethodEventMark::JvmtiMethodEventMark+0x40 (jvmtiexport.cpp:235)
V [jvm.dll+0xad53d6] JvmtiCompiledMethodLoadEventMark::JvmtiCompiledMethodLoadEventMark+0x46 (jvmtiexport.cpp:1062)
V [jvm.dll+0xad1752] JvmtiExport::post_compiled_method_load+0x232 (jvmtiexport.cpp:2162)
V [jvm.dll+0xa52a80] JvmtiCodeBlobEvents::generate_compiled_method_load_events+0x90 (jvmticodeblobevents.cpp:241)
V [jvm.dll+0xabef70] JvmtiEnv::GenerateEvents+0x50 (jvmtienv.cpp:3552)
V [jvm.dll+0xa6c231] jvmti_GenerateEvents+0x1e1 (jvmtienter.cpp:5420)
C [jvmtiCompiledZombie.dll+0x1047]

It can be easily reproduced with slowdebug build with the following command:
java -agentpath:jvmtiCompiledZombie.dll -Xcomp -XX:ReservedCodeCacheSize=20m -XX:+ZombieALot -jar SwingSet2.jar

The agent source is attached.