While I admit that it is inconvenient for testing/debugging, if you package your project as a “Shipping” build, it will work with Electra.
What you see as a “crash” is merely a check() condition that triggers. Since these checks are all disabled in shipping configurations your project should then work with your 601 videos and Electra.
When you say the WmfMedia “freezes”, how exactly does that manifest itself? Is the entire application blocked or is playback not progressing?
If there is audio in the videos, does the audio continue to play and it’s just the video that does not advance?
If you set the LogWmfMedia log category to VeryVerbose (and maybe the LogMediaUtils as well), do any of the log messages at the time of the freeze indicate what might be happening?