Found this in a personal run on Mach5 with ZGC which seems to be unrelated to my changes:

#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (c:\sb\prod\1684909938\workspace\open\src\hotspot\share\gc\z\zMark.cpp:330), pid=76628, tid=44564
# assert(!finalizable) failed: Can't handle finalizable marking of nmethods
#
# JRE version: Java(TM) SE Runtime Environment (21.0) (fastdebug build 21-internal-LTS-2023-05-24-0630532.christian.hagedorn.jdk-test)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 21-internal-LTS-2023-05-24-0630532.christian.hagedorn.jdk-test, mixed mode, sharing, tiered, compressed class ptrs, z gc, windows-amd64)

Current thread (0x00000225e457f7a0): WorkerThread "ZWorkerOld#2" [id=44564, stack(0x00000035fab00000,0x00000035fac00000) (1024K)]

Stack: [0x00000035fab00000,0x00000035fac00000]
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [jvm.dll+0xc56141] os::win32::platform_print_native_stack+0xf1 (os_windows_x86.cpp:236)
V [jvm.dll+0xee5f77] VMError::report+0x1467 (vmError.cpp:966)
V [jvm.dll+0xee82b5] VMError::report_and_die+0x645 (vmError.cpp:1758)
V [jvm.dll+0xee89c4] VMError::report_and_die+0x64 (vmError.cpp:1523)
V [jvm.dll+0x550fcb] report_vm_error+0x5b (debug.cpp:191)
V [jvm.dll+0xfb7c5a] ZMarkBarrierFollowOopClosure<1,2>::do_nmethod+0x6a (zMark.cpp:330)
V [jvm.dll+0x79e515] stackChunkOopDesc::iterate_stack<0,OopIterateStackChunkFrameClosure>+0x145 (stackChunkOop.inline.hpp:232)
V [jvm.dll+0x79fadb] InstanceStackChunkKlass::oop_oop_iterate_stack_slow+0xab (instanceStackChunkKlass.cpp:158)
V [jvm.dll+0xfb6f43] InstanceStackChunkKlass::oop_oop_iterate_stack<oop,ZMarkBarrierFollowOopClosure<1,1> >+0x303 (instanceStackChunkKlass.inline.hpp:135)
V [jvm.dll+0xfb18cf] InstanceStackChunkKlass::oop_oop_iterate<oop,ZMarkBarrierFollowOopClosure<1,1> >+0xdf (instanceStackChunkKlass.inline.hpp:67)
V [jvm.dll+0xfb096b] OopOopIterateDispatch<ZMarkBarrierFollowOopClosure<1,1> >::Table::oop_oop_iterate<InstanceStackChunkKlass,oop>+0x5b (iterator.inline.hpp:111)
V [jvm.dll+0xfae04b] OopOopIterateDispatch<ZMarkBarrierFollowOopClosure<1,1> >::Table::init<InstanceStackChunkKlass>+0xcb (iterator.inline.hpp:115)
V [jvm.dll+0xfaef71] ZIterator::oop_iterate<ZMarkBarrierFollowOopClosure<1,1> >+0x1f1 (zIterator.inline.hpp:55)
V [jvm.dll+0xfb96ca] ZMark::mark_and_follow+0x3fa (zMark.cpp:457)
V [jvm.dll+0xfb8e48] ZMark::follow_work+0x1d8 (zMark.cpp:661)
V [jvm.dll+0xfbb5af] ZMarkTask::work+0x1f (zMark.cpp:935)
V [jvm.dll+0xf30567] WorkerThread::run+0x97 (workerThread.cpp:196)
V [jvm.dll+0xe569cd] Thread::call_run+0x1cd (thread.cpp:222)
V [jvm.dll+0xc54aa2] os::win32::thread_native_entry+0xa2 (os_windows.cpp:551)
C [ucrtbase.dll+0x26b4c]
C [KERNEL32.DLL+0x14dd0]
C [ntdll.dll+0x7e3db]