JDK9 javac recently started writing the JDK9 version tag into class files (it was using the JDK8 version). This now causes the ASM library Byteman relies on to break whne Byteman is fed a file compiled by javac with target level 9. Byteman needs to move on to a later version of ASM which works with JDK9 class files. Unfortunately no such ASM release is available at present.
Until that code arrives the only workaround is to generate code with target level X where X < 9.