Please! Someone help me!

Using WinCC v7.4 SP1 

Does anyone have experience with 8+ Modbus TCP-connections into WinCC? I want to collect VFD data from up to 8 VFD. I am using RS485 to Ethernet converter and configured driver for MODBUS TCP/IP with one Ethernet address and different Slave address(DA), when i am communicating with one VFD then status of driver connection is OK,  but when communicating multiple VFD, then status of connection driver showing Disconnected for all except 1 VFD(which is also some time showing disconnected) while i have tested all VFD communicating over MODSCAN at a time with remote TCP/IP connection and found OK.

So does anyone have any tips or experience with this solution on this scale? 

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