Hi, try looking through your download's and finding the plugins you downloaded from BSMC. The files should have -CRACKED at the end of them, from there you need to find which plugins are on your server.
Take them all out of your server and add one at a time until you find the culprit.
Also there has been an issue lately that support for Java 9 has been quite broken. If you happen to be using Java 9, I recommend you downgrade to Java 8, that could even fix your issue.
I'm trying to download version 6.4.0 but it won't let me. I click the 6.4.0 version and it just sends me back to the page. I can only download the latest version.