Playing my first campaign with Ptolemaic Empire and absolutely loving it, except for one thing: Bribery.

The seleucids were successful in bribing my settlements Side, Halikarnassos and the other city in asia minor/anatolia/cilicia and I had to take them back. They were constantly trying to do it again and my assasins failed killing the diplomat multiple times but I was able to cripple their economy in the war so their attempts stopped for the time.

Many turns later and I'm suddenly in war with Pergamon who immediately were successful in bribing Side. Of course I can take it back again but I would rather be able to somehow turn off or remove their ability. The whole thing about marching armies back and forth and repeating these battles are not fun, breaks the immersion and makes the game more tedious instead of challenging.

The settlement Side is at a 155% happiness without an governor but they still are able to bribe it over and over again when i reload the save and I wan't to remove the diplomat/heavily reduce the ability to bribe. I don't use the mechanic myself so I dont care if it applies to everyone.

How do I achieve this? I've been looking in the forums for hours but can't find a good solution. I've been poking around in the folders but I'm not experienced in this and actually have no idea what I'am doing, any suggestions?