Hi Jen,

Ben's suggestions are good ones- his approach should make your code execute more consistently, and may fix your problem. That said, there does appear to be a product bug in that your original code was able to intermittently cause a server-side error. I've entered a bug in our issue tracker to address this problem:
https://www.labkey.org/issues/home/Developer/issues/details.view?issueId=12191

Please let us know if Ben's modifications aren't enough to get you up and running in the short term. And thanks, Ben, for jumping in and helping out!

Thanks,
Britt