Modem Nodes "failed to connect" in Node Red

Hi community. We have an installation of 40 temperature & humidity wireless enterprise sensors which at first we tried to connect with 1 ethernet modem (with lantronix chip) to transmit the data. As this proved to be inadequate due to the topology of the installation we ordered additional modems (4 ethernet & 1 usb of the recent designed-new chipset non-lantronix).
Almost at the same time we noticed that the modem-nodes in Node Red started failing. Displaying a “Failed to connect” message while adding a debugging node on each shows that we keep receiving data.

Any idea what causes it and what needs to be done?