Weintek HMI MT8000i ethernet problem

I have been working with a PLC which has three WEINTEK MT8000i TouchScreens and a computer with an ICONIXS SCADA and an OPC server.
Everything is connected to a switch and every element has a static IP adress!

Now, simetimes during operation, the computer with the OPC server loses communication with the PLC. During this time the Weintek Touchscreens still function.
I even had a couple of instances where the switch stoped funtioning for a couple of minutes.
The WEINTEK Touchscreens use Modbus TCP and someone told me that they may flood the communication.

Has anyone had this problem or knows something about weinteks???

thanks