SAP reported there were assertion failures since 2019-07-14.
It looks like traversal specific.

#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/usr/work/openjdk/nb/linuxx86_64/nightly/jdk/src/hotspot/share/gc/shenandoah/shenandoahCodeRoots.cpp:319), pid=17233, tid=17264
# Error: Shenandoah assert_correct failed; Object klass pointer must go to metaspace

Referenced from:
  interior location: 0x00007fb755390a7f
  outside of Java heap
  0x00007fb755390a7f is at entry_point+3807 in (nmethod*)0x00007fb75538ed90

Object:
  0x00000000ffdc0d08 - safe print, no details
  region: | 2039|R |BTE ffdc0000, ffe00000, ffe00000|TAMS ffe00000|U 256K|T 0B|G 256K|S 0B|L 0B|CP 0|SN 0, 0, 43e8, 43e8

Current thread (0x00007fb744001000): GCTaskThread "Shenandoah GC Threads#1" [stack: 0x00007fb74ce30000,0x00007fb74cf30000] [id=17264]

Stack: [0x00007fb74ce30000,0x00007fb74cf30000], sp=0x00007fb74cf2c550, free space=1009k
Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x18e5c0f] VMError::report_and_die(int, char const*, char const*, __va_list_tag*, Thread*, unsigned char*, void*, void*, char const*, int, unsigned long)+0x37f
V [libjvm.so+0x18e6a0f] VMError::report_and_die(Thread*, void*, char const*, int, char const*, char const*, __va_list_tag*)+0x2f
V [libjvm.so+0xa857b1] report_vm_error(char const*, int, char const*, char const*, ...)+0x111
V [libjvm.so+0x15d443c] ShenandoahAsserts::print_failure(ShenandoahAsserts::SafeLevel, oop, void*, oop, char const*, char const*, char const*, int)+0x52c
V [libjvm.so+0x15d51d7] ShenandoahAsserts::assert_correct(void*, oop, char const*, int)+0x137
V [libjvm.so+0x15ff8b5] ShenandoahNMethod::assert_alive_and_correct()+0x165
V [libjvm.so+0x1601461] void ShenandoahCodeRootsIterator::fast_parallel_blobs_do<true>(CodeBlobClosure*)+0x111
V [libjvm.so+0x16ac2e1] ShenandoahRootScanner<ShenandoahCsetCodeRootsIterator>::roots_do(unsigned int, OopClosure*, CLDClosure*, CodeBlobClosure*, ThreadClosure*)+0x1f1
V [libjvm.so+0x16ac643] ShenandoahInitTraversalCollectionTask::work(unsigned int)+0x203
V [libjvm.so+0x195a2c0] GangWorker::loop()+0xe0
V [libjvm.so+0x1823d46] Thread::call_run()+0xf6
V [libjvm.so+0x1426186] thread_native_entry(Thread*)+0x116