Error Message "Unable to Evaluate Play Request Code: -1"

Plex Players Streaming Devices
1

1) IMG_3755
1) IMG_3755481×1041 50.1 KB
2) IMG_3756
2) IMG_3756481×1041 82.5 KB
3) IMG_3753
3) IMG_3753481×1041 46.4 KB
Server Version#: 1.19.3.2831 – 181d9145d (Synology)
Player Version#: iPhone app re-installed 5/20/2020
Error message in mobile app (iPhone AND iPad)
A brand new error message has emerged, after many months of flawless playing. It appears only on the mobile apps, and not on the Mac PLEX app; and not on playing through a browser.

I have enclosed screenshots from the iPhone app, showing that when in the “ Folder ” view, the view that I most love to use: “ Unable to Evaluate Play Request. This type of metadata is not supported for PMKMetadataPlayRequest Code: -1 ”

Without ANY change in any of the metadata in the prior year, when the app functioned flawlessly, suddenly comes the new error message that the same metadata is suddenly now “unsupported.”

Plex media server on Synology NAS is updated to version 1.19.3.2831 – 181d9145d
I deleted my iPhone app and then re-installed anew….to no avail.

Please suggest a solution to this new problem, so that I can continue using “Folder” view to access files. Many thanks.