ModBUS TCP/IP Issue - Multiple Connections

Forgive my ignorance - I am not a ModBUS programmer, but I am working with somebody who is, and we cannot figure out this problem.

We have just replaced 9 large 750kva UPS's batteries with new Samsung Lithium Ion Cabinets at a Data Center. These new cabinets all have ModBUS TCP/IP - and we are able to read the values off of the WebCTRL interface without any problem. Unfortunately, the software we were provided to monitor these cabinets via web interface, only works if we disconnect the cabinets from WebCTRL completely. Clearly, we want to be able to receive alarms through WebCTRL so we can notify the facility team...but we also want to be able to connect to the cabinets via the web interface as it provides a nice, easy interface for staff to be able to locate the exact problem. It's like the cabinets can only send out data to one connection at a time...which...according to Samsung, they can do many simultaneous connections. These are the cabinets --- We have all of the new cabinets on a BMS network switch, all with static ip's and proper reporting back to WebCTRL via ModBUS TCP/IP. We can always ping the cabinets, we just cant connect to them unless the webctrl session is terminated.

Anyone have any clue what could be happening?
I'm not familiar with WebCTRL... but are you using a win 10 based OS to view the web client? It might be that Windows firewall is preventing the communication between the client and its server.. might consider adding these as "exceptions" in Windows Firewall?