For some reason recently I've had the problem of when I put one thing down on a route with my mouse, it actually puts down two items, even though I clicked the mouse once, and this is in TRS19, not TRS22.
All my mouses are wired, not Bluetooth or WiFi, and I have never experienced that problem except for an accidental double click with the left button while the Add tool is active.
I do recall some users having problems with using WiFi or Bluetooth for their mouse and/or keyboard connections but I am unaware of anything in Trainz that would be specifically different for non-wired input connections. So my suspicion would be a driver update or a WiFi/Bluetooth specific Windows setting.