The following snippet of code will generate errors. The type of error is random, but it's one of the following: java.util.ConcurrentModificationException, java.lang.NegativeArraySizeException, or java.lang.NullPointerException. I've battled with these errors in my application for a while now, but I've only recently been able to narrow down the problem to using a virtual mapping to an S3 bucket inside of a cfthread block. Knowing that, I was able to write a test that reproduces the problem. I have also includes some example stacktraces, though, sometimes cfcatch does not provide one. In that case, I provided a screenshot of <cfdump var="#cfcatch#">.
Stack traces from test code
Example stack trace from production application
I have tested this in the following environments:
Lucee 188.8.131.52 on Windows 10
Lucee 184.108.40.206 in Docker on Amazon Linux EC2