If Pre-Rec option is enabled in VMS, then it is not possible to add/remove camera as the camera status will become an orange ticked box. Because when Pre-Rec option is enabled, VMS will start creating video file. To avoid VMS creating files and the camera then being removed and cause software error, Pre-Rec must be disabled because camera can be added or removed.
Below is a list of camera status in camera install of VMS for reference.
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