No- your object is not broken. Before I sell any object I verify it is working with friends. Most commonly the problem deals with sits. This is not a product problem this is a Second Life problem.
"No Sit" is because of this bounding box issue with large sculpted objects. Fun stuff I know. Here are some tips to be able to use the products you have purchased to their full potential. Do not put anywhere near large sculpted objects. Including and not limiting: Palm trees, Mountains, and Sculpted Roofs.
If you would like me to prove your item you purchased works let me know and I can teleport you to a sandbox to rez and test. If you do not need me to test then please create a platform out of a prim way up in the sky not near anything and rez your product. You will find that your product works great and is not broken.
My products use the perfect sitter, which means I have multiple sits per prim. That is how my products have so few prims with so many sits inside of them.
Below are 2 Jira's that have been opened that deal with this issue:
http://jira.secondlife.com/browse/SVC-5501
http://jira.secondlife.com/browse/SVC-3811
