Flickering subtitle time stamp in MKV files

I have multiple WDTV boxes in my house. WDTV+ on older firmware, WDTV Live Streaming on 1.03.?? and a Live Streaming on the latest firmware, and all 3 have the same problem. What’s goins on is, if I take an AVCHD MTS file from my high def camcorder and rename it with a .MKV (yes, you can do this…MTS and MKV are just containers)…the video plays fine no matter what but whether it’s an MTS or MKV file, if I turn on subtitles, the date/time stamp is shown in the bottom left corner but it flickers. Like maybe .5 seconds on, .5 seconds off, etc etc. But, if I create a BD ISO from the folders on my camcorder and watch the ISO file back and turn on subtitles, the date/time stamp stays solid when it’s on. What is producing the flickering when watching back individual files? When I view the same MKV in VLC on my PC and turn on subtitles, the date/time stamp is solid with no flickering so this leads me to believe it’s a WDTV problem.

Any ideas to eliminate the flickering?

No, you can’t just rename an m2ts to mkv since they are completely different containers. You’re lucky it plays at all since it supports both containers but this may well be the reason your subs are flickering.