Symptoms
In Microsoft Skype for Business Server 2019, .etl files are produced when CLS logging is running. However, after the CLS logging is stopped, the centralized logging service agent creates new .etl files and continues to write to the .etl files.
Resolution
To fix this issue, install the December 2019 cumulative update 7.0.2046.151 for Skype for Business Server 2019, Centralized Logging Service.