I can share your frustration as it took me a long, long time to make it work through trial and error settings on the Codec Tweak Tool.
I think you need to open it and patiently go through each setting one at a time and change it then try to play it on the karaoki and undo if fail and repeat until something magically clicks.
I think the ones you need to change will be the ones associated with MP4s.
I can’t believe after all these years this problem is still going.
Give it a try and good luck.