SQL Anywhere Long Varchar/Binary Column Length Limited to 32767
Found the answer:

The issue was not with SQL Anywhere, but rather in our server datasource administration settings.

We use ColdFusion 10 on our web server, and the datasources have a Long Text Buffer setting which was limiting the size of the string being returned from a query of the database to 64000

Changing this value to 2000000 solved the issue.