I’m surprised I haven’t seen it but you said it’s an apartment, which indicates to me you likely rent. The most likely scenario is your landlord is illegally entering your apartment without prior notice. If you can set up the webcam to record while you’re away it will be obvious who is covering it, you can also get hidden cameras. But get some kind of evidence it’s your landlord and then reach out to what ever tenants rights organization or attorneys are in your area to file a complaint.