AIDA64 detects the current Windows Desktop layout when you start it up, and when it detects that the previous position where you've left the SensorPanel at no longer falls into the visible Desktop area, it will reset the position to (0,0) -- which is the top-left corner of the primary monitor. In your case the problem might be that when AIDA64 starts up, Windows still didn't restore the previous Desktop arrangement, and the Desktop area doesn't yet cover the secondary display. Can you please check if the issue only happens when you restart (or cold start) your computer, or it happens also when you keep your computer running and only restart AIDA64?
You can move them to the desired location by altering the SensorPanelPosX, SensorPanelPosY, OSDPosX and OSDPosY values in the Registry, under HKEY_CURRENT_USER\Software\FinalWire\AIDA64.