DISABLED subtitles cause stuttering/laggy video

[Adoniram]

Hello All,

Recently, I noticed some files will start showing a great deal of stuttering or jittery video behavior. More specifically, if I disable subtitles in UMS, I get something like 5 frames per second for the duration of the video. However, if I enable subtitles, it plays fine, but if course I have annoying subtitles... This only happens on some files, not all. It seems a codec or something is being used, suppressed, and hogging either CPU time or bandwidth, or God knows what else...

Attached are trace logs for versions 5.5.0 and 6.0, the results being identical...
(did a clean install for version 6.0)

Setup:
-WIRED gigabit connection between PS3 and desktop computer
-PS3 has HDMI to Onkyo receiver
-Computer running Windows 10 x64
-Java version 8 update 71 (just updated before test)
-Transcoding quality set to automatic (tried multiple settings other than this as well)
-Maximum transcode buffer size: Tried various values (200, 400, etc); no difference

Any help troubleshooting this is greatly appreciated!

note, I only play the file for a few seconds because that's all it takes to see it's screwed up... (I've tried letting it play for 10 minutes, or fast-forwarding ahead... no change)