Well, I just had a look and believe it or not, the background fit checkbox was already ticked on. I ticked it off, then back on again, re-rendered and got the same result. Hmmmmm..... I just wonder about this. I never had a problem like this with Poser 5.
I'll go ahead and place it on a flat plane prop and re-try it.

Here's the link to my freebies:   https://www.renderosity.com/mod/freestuff/?uid=493127

My cousin Jack can speak to beans. That's right.... Jack and the beans talk