Microsoft has acknowledged that there is a known issue with its latest Windows 10 update. Some users have reported that the seek bar in Media Player has become inoperable after downloading the new patches. The issue corresponds to KB4467708 (OS Build 17763.134) that applies to the now somewhat notorious Windows 10, version 1809 (October 2018 Update).
https://www.notebookcheck.net/Microsoft-Windows-10-update-affected-by-Media-Player-bug.366416.0.html