On version 7.5.6 and just had an issue with 10 or so tags from an SLC going to ‘unreachable’ red crosses etc although another 10 in the PLC were reading correct.
Disabling a tag and re-enabling cured it as did doing the same for the PLC connection as a whole.
The SLC is being read through a MOXA gateway onto Ethernet.
Is there any explanation as to what could have caused this? No PLC mods occured in this PLC.