assert(false) failed: Non-balanced monitor enter/exit! Likely JNI locking

AgentVM Threads crashes with
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (t:/workspace/open/src/hotspot/share/runtime/objectMonitor.cpp:875), pid=14180, tid=10896
# assert(false) failed: Non-balanced monitor enter/exit! Likely JNI locking
#
# JRE version: Java(TM) SE Runtime Environment (12.0+21) (fastdebug build 12-ea+21)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 12-ea+21, mixed mode, tiered, compressed oops, g1 gc, windows-amd64)
# Core dump will be written. Default location: T:\testOutput\test-support\jtreg_open_test_hotspot_jtreg_tier1_compiler_not_xcomp\scratch\2\hs_err_pid14180.mdmp
#
# If you would like to submit a bug report, please visit:
# http://bugreport.java.com/bugreport/crash.jsp
#

--------------- S U M M A R Y ------------

Command Line: -Djava.library.path=c:\ade\mesos\work_dir\jib-master\install\jdk\12\21\windows-x64-debug.test\hotspot\jtreg\native --patch-module=java.base=T:\testOutput\test-support\jtreg_open_test_hotspot_jtreg_tier1_compiler_not_xcomp\patches\java.base -Djava.security.policy=file:/t:/testOutput/test-support/jtreg_open_test_hotspot_jtreg_tier1_compiler_not_xcomp/jtreg.policy com.sun.javatest.regtest.agent.AgentServer -allowSetSecurityManager -port 62063 -timeoutFactor 4.0


--------------- T H R E A D ---------------

Current thread (0x00000015261b0000): JavaThread "AgentVMThread" [_thread_in_Java, id=10896, stack(0x0000001526740000,0x0000001526840000)]

Stack: [0x0000001526740000,0x0000001526840000]
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [jvm.dll+0xb4b961] os::platform_print_native_stack+0xf1 (os_windows_x86.cpp:369)
V [jvm.dll+0xd68a70] VMError::report+0xe80 (vmerror.cpp:698)
V [jvm.dll+0xd6a2c4] VMError::report_and_die+0x854 (vmerror.cpp:1471)
V [jvm.dll+0xd6a984] VMError::report_and_die+0x64 (vmerror.cpp:1295)
V [jvm.dll+0x5783de] report_vm_error+0x7e (debug.cpp:232)
V [jvm.dll+0xb238c4] ObjectMonitor::exit+0xf4 (objectmonitor.cpp:1025)
V [jvm.dll+0xc109ca] SharedRuntime::complete_monitor_unlocking_C+0x17a (sharedruntime.cpp:2062)
C 0x000000157617648f