I noticed this a few months ago, but it's getting kinda annoying to the point where I decided to report it.
For some reason some of my K9 or Supervisor units will be unable to patrol or respond to calls because "there is no assigned personnel or trained personnel" when there is. I've tried reassigning the same personnel, turning the unit off and on, but the only solution seems to be is training new personnel. This seems to only happen to stations that I have built 2 years ago.
Screenshots