If you are using AppDynamics 4.5.17 or a lower version and the application is displaying “BadImageFormatException: Bad method token” error, please update your AppDynamics. There is a known issue with 4.5.17 and lower versions.
This issue occurs intermittently. IIS reset temporarily solves it. In the case I worked on, it was happening on all IIS servers. There were not any recent Windows updates or code deployments.
Certain versions of AppDynamics causes application crash. This known issue is reported in their documentation.
You can also collect a dump file to make sure the issue is caused by AppDynamics.