MP4 files hang when trying to open

For the last 3 builds, MP4 files hang the system and are not able to open (or takes 15 minutes to open).

Scenario: I have a folder that I download MP4 videos to.  Starting 3 builds ago, if I try to open the folder with MP4 in it... it just says working and takes minutes to index folder(I usually have to end the task manually)  If I try to right click on file, it just hangs.  If I single click to open with windows media player it takes minutes before it will play (if at all).  This folder is a local folder and not mounted.  I have had to revert to previous build.  The problem was introduced after version 1809 (OS build 18298.1000).  I have not tried the last 3 builds after this and they all have the same problem.  I even tried to delete the folder completely, then created an new one and downloaded an MP4.  Same problem, with just 1 file in the folder it just hangs when indexing the folder.