Leaking sensitive details to a friend group. Public and private subversion of administrative decisions. Slipping in new rules and practices and fighting dirty social games. These are cases I have seen and would imagine with this question.
Leakers are tricky. Of course many have to also be good workers, just their outlet is terrible for security, goes around the block (at worst spreading to banned members and fanning fires), and fuels us/them drama and the sort of
cliques I've gone on about. You basically have to play the highschool game to deal with them short of just ripping them out when you're sure it's them, and weathering the inevitable storm. It helps to have a strong practice of non disclosure and a consistent approach. Rest on an ironclad case, it's the grey zones when they get zingers on the upper management that you really have a mess.
Now you can imagine I'm strong willed at times. I have no issue arguing with owners, including when I know they have a trigger finger. There are distinctions. In public the line of subversion is crossed when you have a member representing the site being rude, directly contradictory, 'no you're wrong this is how it should be', and so on. I firmly believe in staff sticking together, it helps in matters of point 1. By all means disagree, but if it is public be civil, remember your position and consider if your grind is better off dealt with in private. Failure to do this is when you have a problem. If reminders and a sitdown doesn't work then maybe it's time to let them go. I set a higher bar for this in private but again, you can cross a line where the criticism is downright disrespectful, seriously degrades the image of people who are just trying to make things work, and causes constant stress because argument after argument. Invariably this also requires a sitdown and if that doesn't do it then it's probably time to go.
Sometimes you get a very promising person who you decide to promote because they clearly know their stuff, and they do. But you haven't realized their vision is very different from yours. They implement things their own way, it may contradict you. This can be more blurry, they may believe they're doing right and aren't intending to subvert you, they aren't actually disloyal. Ideally the staff area has a blurb that makes boundaries and agency clear so this is nipped from the getgo, on top of a nice chat and maybe a little q&a. Having an idea of what they want to see before they go on board is good. If it still happens perhaps a sitdown and reminders will do it. But eventually you might realize it's not going well and it is again time to part ways.
In all these cases you are best served when you've kept your administration clear and coherent. You avoid giving ammunition in public and in private. People are not working with misconceptions, boundaries are known, ground rules are set. Give the benefit of the doubt and keep an open mind, even be willing to compromise on behalf of someone who really does help, but be prepared to make a tough choice when it's clear what the staffer wants does not line up. You need to think of a line and set it because giving them leeway can run out of hand and give them ammunition instead.
And try not to let large portions of the site exist on the back of very few people. This is a general principle but if you have a fickle or strong willed staffer running something important, making all the art hosted on their external site whatever, and then oops it doesn't work out, you're screwed. Resiliency is key. You need to expand and contract based on what can be supported now, and have contingency if you have less to work with later. I think it's poignant to mention here because again, some of the hardest workers can also have the widest range in attitude, culminating in blowouts that are magnified by their contributions to the forum if not carefully kept in mind.
