Hello Steve,
thank you for your reply.
In few days I will be back to the customer plant and will be able to make some tests on the PLC.
But your explanation sounds reasonable, as I have already checked that the subscription update rate in the PCo agent was set to 1000ms (default value)...definitely too much to intercept PLC tag change.
I will get back to you soon with some feedback.
with regards
Mauro