Green Sscreen with some MKV movies

[joesphotovideo_gmail_com]

Server Version#: 1.14.0.5470
Player Version#: Webapp, Firestick and others
Synology DS918+ with Win10pro

I have several movies that although they play fine in Windows Media Player or other apps such as Windows Movie & TV, they only display Green with Audio through Plex.

I have run all Windows Updates
Tried two different versions of PMS (1.13.9.5456 and 1.14.0.5270)
I have shut everything down and restarted
I’ve tried it at difference transcoding and quality settings
I updated my nVidea drivers. (Was running Windows Native as well).
I tried deleting the Codex in the folder and let Plex update them.

I tried logging it at different logging settings but after clearing out the log and then attempting to play a video with the problem it logs nothing but it went to load it and communication back and forth.

I’m open to other suggestions if any on what else to try. It’s not a big problem and only a few MKV movies with MPEG-2. Am I Missing another Codex?

Thanks

[joesphotovideo_gmail_com]

An update: Still don’t know why this issue is occurring but in the meantime I converted (with Handbrake) the MKV files to MP4 and they now play fine. Fortunately I only have a couple MKV files that are causing the problem. Strange thing though is I have many MKV files that work fine.