I just upgraded our spark version from 1.4.1 to 2.0.0. Upon running a job (which worked perfectly with 1.4.1) to test it, I see that it fails with an assertion error:

"assertion failed: copyAndReset must return a zero value copy”. I saw a thread related to this on StackOverflow, however, I could not find any code or dependency in our codebase that implements the old Accumulator. We do not use SparkRunner either. 

What are some other reasons I would be seeing this error?