Unable to add entities to datatable when subscribing on data chaged of IsConnected property

Hi There

I am trying to add some entities to a datatable when a remote thing isConnected property is changed

so my subscription code look like that (it is only one line):

me.AddConnectionLogEntry();

AddConnectionLogEntry - is a service on my thing itself

this service adds some entities to my datatable

when I disconnect my remote thing - I get an exception

Execution error in service script [0315.0134628e10 AddConnectionLogEntry] : Wrapped java.lang.Exception: Unable to add table entry: null Cause: Unable to add table entry: null

But when I trigger it from the thing itself - everything works

another strange thing :

I tried to make the same subscription on a boolean property that I made by myself

and it works ( with the same subscription code and the service "AddConnectionLogEntry" was the same too)