The jvmti class redefinition creates temporary scratch classes for it's own purposes. These classes are added to corresponding classloaders and might be unloaded.
In this case the jvmti/jfr and log events are generated twice: for original class and for it's scratch.

The bug could be reproduced by jfr test
jdk/jfr/api/metadata/eventtype/TestUnloadingEventClass.java
with '-Xcomp -XX:TieredStopAtLevel=1' or with '-Xcomp'

The test hang because got 2 events while waiting for one.