Splunk AppDynamics limits the number of registered error types (based on error-logging events, exception chains, and so on) to 4000. It maintains statistics only for registered error types.

Reaching the limit generates the CONTROLLER_ERROR_ADD_REG_LIMIT_REACHED event. While it is possible to increase the limit, we recommend refining the default error detection rules to reduce the number of error registrations to have the error you are not interested in capturing ignored.

For more information, see information on configuring log errors and exceptions to ignore in Error Detection.