I'm running IWS 7.0 and used the KOYO driver to communicate with my PLCs to read thermocouple and 4-20mA data and to date, I have never experienced your symptom. My PLCs scan time is typically less than 12ms. I would start by monitoring the suspect values on your PLC Data View table. If the values are good, try monitoring your network data to see if there're any hiccups , i.e. crashes that may introduce a delay of some sort.
Hope this helps