The following assert in HeapShared::init_subgraph_entry_fields() if classes are being transformed using a java agent during dump time:
      assert(InstanceKlass::cast(ik)->is_shared_boot_class(),
             "Only support boot classes");

Stack: [0x00007f6f47128000,0x00007f6f47229000], sp=0x00007f6f47227930, free space=1022k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0xdcfd54] HeapShared::init_subgraph_entry_fields(JavaThread*)+0x344
V [libjvm.so+0x14694ac] MetaspaceShared::preload_and_dump_impl(JavaThread*)+0x7c
V [libjvm.so+0x146967b] MetaspaceShared::preload_and_dump()+0x10b
V [libjvm.so+0x18bdfad] Threads::create_vm(JavaVMInitArgs*, bool*)+0x9fd
V [libjvm.so+0xfb7d88] JNI_CreateJavaVM+0x98
C [libjli.so+0x3b3f] JavaMain+0x8f
C [libjli.so+0x7d19] ThreadJavaMain+0x9