When you tried to download the session log, the file name is "DownloadLogServlet".
And then, the file's size is 0 bytes after downloaded
AS per Technical Document 264934 the cause is not having enough memory on this server, the server has 16 Gb RAM, we recommend 64Gb.
The solution would be to increase memory to 64Gb, or purge logs to reduce the load.
You can use a workaround that is creating a filtered report, the report works for specific filtering you need
Inside session logs, in the right side you have reports buttom, you can customize a report with the session log needed rows