The problem of the image showing like the following:
Normally if this problem occur, need check the issue from different points.
If the distance is too long, or the cable used is poor, such as the extension cable of the camera does not use a shielded cable, or the connection is virtual, or the wiring environment is more susceptible to interference, it may cause the camera signal to weaken and the signal may not work properly Transfer to the recorder.
It may be that the power supply is interrupted at intervals, or it may be the charging and discharging process of the internal components of the camera.If this problem occured, you can disconnect and then connect the camera to the MDVR again to check if it can work, if it can work, mostly, it maybe the camera issue.
Firmware issue or board issue:
If finish the communication and camera issue, they are all OK, please tell us, the firmware version you are using and the MDVR model you are using, we will check the problem at our side.