OTGW error, how to solve?

[BartSr]

I am using for a long time an OTGW monitor which gives fine information to Domoticz
but...
The logfile shows up every 30 seconds:

2021-12-06 21:33:17.115 Error: Otgw: Error received!

I like to solve that as I don't want meaningless (for me) errors but how to figure that out?
I am using boiler Remeha Avanta together with thermostat iSense and Schelte's OT monitor

Any idea?

TIA -Bart