How can I deal with the group who are just ever complaining, and theft cases among the members?
Two completely separate issues, let’s take them one at a time.
First, the complainers.
What are they complaining about? Have you listened to them? Do they have some fair points? Even if they just like complaining, the best thing to do to placate them is to take some time out and show them you have listened and acted accordingly.
Then after that, if they continue to complain without good reason, you are justified in asking them to stop.
Or appoint somebody to handle and filter complaints for you, perhaps a supervisor. Brief them to deal with the small matters and to bring anything serious to your attention.
The theft cases. That is a serious issue, which you should address. Having a thief amongst you will unsettle everyone and create a very bad atmosphere. How you handle it depends on who is stealing what from whom.
But first be very sure of your ground. You don’t want to accuse somebody of theft on the basis of gossip. Do you have evidence, witnesses, a number of reputable people willing to back you up ?
Is this an employee stealing from you? Or from other employees? Again, I really can’t be specific without more information.
You have said “among the members “so I have to assume someone is stealing from your team. Is this a club?
Are the thefts serious? Do you have a policy? Once you have checked the facts out carefully, make sure everyone knows that you are aware of what is happening, that you will not tolerate it, and that if you find the culprit they will lose their job/membership, and you may involve the police. Make sure there are lockers available where people can store valuables, and ask everyone to be vigilant.
Sorry I can’t be more specific. Can all readers please let me have enough information to respond if they submit a question.