As I said last week, the first stage of troubleshooting is understanding any data available, and getting a feel for the margins of error attached to it. The data has to be supplemented with on-site testing, noting the appearance, odours, and residual evidence of past problems of the plant, and structured questioning of staff.
Once all of the data has been gathered and analysed, it is usually the case that there are a number of overlapping problems. It if frequently the case that the problems are worse than the client thought they were.
However, everything is possible in engineering. Problems can always be fixed, though this is not always as cheap or quick as clients might hope.
However, it is often the case that at the point where I troubleshoot a plant, several attempts have been made to apply cosmetic or superficial fixes. Though these may be individually cheap, they often add up over time into more than it would have cost to get to the bottom of the problem as soon as it manifested.