What comes at you too fast? How do people know you are a process control engineer? What is more disturbing than talk shows? Is a flea market indicative of a project behind schedule? These and other questions you have not asked will be answered.
How do you know when interaction is going to be a problem? Why would the control loop design need to be changed? Are there hidden loops? What can you do with tuning to mitigate the problem? When do you need to move on to Model Predictive Control? Hopefully, this blog...
Since most unit operations have multiple loops and streams, interactions can exist where the PID output of one loop affects the PID process variable of another loop and vice versa. Interactions can cause loops to confusingly burst into oscillations.
If there were no unmeasured disturbances, feedback control would not be necessary. Process engineers and operators could home in on the best PID output and just leave it at this value. In fact many process engineers are much more comfortable with setting a stream flow per a process flow diagram...
The use of the term "process dead time" can mislead us in terms of recognizing the many sources of dead time. Also we don't often take into effect the profound effect of the speed and the entry point of a disturbance into the process.
Fast oscillations are particularly insidious because the best thing a PID controller can do is ignore them. Action taken by PID controller can do more harm than good in terms of resonance, amplification, and perpetuation leading to increased process variability and premature valve failure.