There are something like 'You notice some of your gold are missing.' in the report. What's it and How to fix?

It means that one of your slaves has stolen gold from you. Check the obedience/loyalty of the slaves you have roaming the mansion. Good help is hard to find these days!

person with rebelious state have tendency for stealing your cash even if they look tammed ;)

https://itch.io/t/606081/i-cant-make-the-due-to-recent-event-rebels-against-your-control

this topic gives few tips how to tame rebelious slaves, for low obedience slave you simply can made her sleep in shackles and maid dress, have fun playing