There are certain times that a dupe who is covered by germs passing a washing tap but do not use them. This happens when a dupe is carrying germ covered materials and shortly after they have dropped this material. The problem reproduces itself massively when different kind of washing tap is lined up adjacent to each other. This happens even if there are four taps and one dupe with germ is passing by them. The same problem doesn't usually happen when dupes were using the toilets, but it often happens after they return from toxic mines. I am playing the Mac version so I am not pretty sure where the log files are created.
Give dupes order to collect a small portion of germ covered material and let them pass through a lineup of washing taps of different kinds (or sometimes the same kind). Put several washing taps in a row adjacent to each other.