At the bottom of the export tab near the export button is a settings button be sure that EXIF data is checked off.
When I took a image file that shows lens data on my Linux system and checked it by right clicking in Windows it showed no lens data. I then open the image in the default image viewer and still no lens data. This appears to be a OS limitation, you could try looking an specialty EXIF viewer for further testing.
If you can see the data with other lens you may want to file a bug report here