I'm sorry to hear about the rendering issues you're seeing with the Jive document preview. This could be due to a number of things and will likely require directly troubleshooting to identify. I would recommend submitting a support case in your private Jive Community customer group and provide along with it a sample file for analysis. Likewise, you may test this against LibreOffice directly to verify if the rendering issues are a current limitation, since LibreOffice is used in the Jive document conversion process.
If you're not familiar with the case submission process, l please reach out to your community manager for guidance.