This sounds familiar to an issue another user had awhile back that the app was unable to clear the temp files due to writing to an external setup and the app could not find the temp files for removal after processing.
Are you just seeing this happen with ProRes LT or any Codec option?
Can you send the logs to the support team for review? help@topazlabs.com
To gather logs, please select Help > Logging > Get Logs for Support and attach the zip file to your reply.
Here is a video to help with the steps of how to collect the logs.