Jython script no longer working after update from 7.1.7 to 7.3.3

[Cole Adams]

I had a jython script as a post function that would automatically set select list fields in JIRA based on information from a database. This is no longer working after updating. I get no errors or anything useful to go on. 

Is there something significant that changed between versions to cause this?

[Nic Brough -Adaptavist-]

I suspect that I know what has changed (the field value storage is now single arrays rather than an option), but you really need to be seeing the error messages JIRA is returning when you try to push values in.

[Cole Adams]

There are no errors in the logs when I try it. The ticket just gets made as normal. What should I look for in the script to change realted to the field value storage?