Thanks for your response. It's no problem, I just wanted to make sure that bug reports are wanted.
Windows 10 Pro 64bit
Vegas Pro 13.0 64bit, build 453 (latest)
It is 100% reproducable in an empty project with one audio track and only Antresol in the chain.
Example with Antresol not as the last plugin in the chain:
I've also considered that it's a bug on the side of Vegas, but none of my other plugins cause this error, which makes it seem related to Antresol.