This is a known issue stated in the release notes section 1.7.1 found here: https://communities.intel.com/docs/DOC-21837
The Workaround stated in the document:
“Reboot your Windows host PC. The USB serial port should then be
present and the IDE will be able to upload sketches to the Galileo board again.”
I know this does not make it less frustrating, but I don’t believe there is not another workaround.