OPC connection sinumerik controller and node red

Hello,

I am reading data from Sinumerik CNC controller and Simatic PLC to Node red with OPC UA.I am using single ethernet for both the controllers.
With Simatic,reading data is happening every time I connect my ethernet.

1.But, for simatic it reads some times and somtimes it dont read
OPC Connection shows endpoint error.

  1. Even, If I have 3 OPC UA connection Node , two OPC UA Node gets connected and one still not able to connect.

Can anyone helps me, why its not getting connected in first place and also why some OPC gets connected and other dont?
Can I read both data

Thank you
Vishal