Opus itself does not decode MP4 content. The problem will be with a video demuxer or codec installed on your system, crashing when asked to decode that particular file.
If you have installed a codec pack (not really needed or recommended these days, in most cases), make sure it's fully up to date. In other situations, updating or replacing individual codecs/demuxers may be needed to avoid the crash with particular files the ones you have installed have problems with.