www.makemkv.com

I purchased the product recently notably to rip ISO files into MKV files so that I can play in Windows Media Player. This appears to be only player to support Dolby Atmos.
I am experiencing issue in that if subtitles (those part of the MKV file, not imported) is on and I skip into the movie.. the video file freezes and CPU temperature escalates.
Even if I move to position desired with subtitles off and then turn on subtitles, machine becomes unstable.
It is a high spec machine i9 12th gen and the MKV files are those of 4k movies. Also with power 3080 gfx card.

Any suggestions.
If I open subtitle file downloaded from internet onto movie, then no issues traversing the MKV file.

Is this happening when you've ripped the movie to a file, or are you using MakeMKV to play the movie from the disk?

Apologies for late reply.
It is the actual MKV files that I generated via Make2MKV , which in turn I am playing on Media Player in Windows 11.

N.B
MKV files are ripped from .ISO files which are typically 50-90GB (those from original Blu-ray discs I suspect).

Windows Media Player seems very confusing at the moment. There's Windows Media Player, which has existed since Windows 95. There's also Windows Media Player which came out in 2022 for Windows 11 but was back ported to Windows 10.

It seems that the new WMP can play .mkv files and I've seen references about it supporting .srt subtitles as a sidecar file. Subtitles on a blu-ray are typically PGS format. I haven't found a reference to wether new WMP supports PGS format subtitles. The program MediaInfo can tell you lots of details about your .mkv files, including what format your subtitles are in. It might simply be the case that the new WMP doesn't support subtitles in PGS format.

I don't have a Windows machine so I can't test on my own.

Just for your information, it is not the legacy one but newer interface one I am using on Windows 11.