Illegal invocation errors are often captured by many different applications. For many applications online this error is sometimes correlated to and triggered by bot activity.
This is not the root cause of the issue but some types of algorithmic website activity is captured. You will often be able to see this activity inside of sessions. If you do see this activity I recommend looking at this documentation for further action:
This can be a difficult issue to solve and we are happy to aid you in this process. Let us know if you need help or assistance on this.