For what it's worth I have seen these CTD's when manipulating naval units however it does not happen every time and so I never determined a common denominator cause. My solution now is just to quick-save (hot key F5) before opening the Force Management screen for naval work and to offer up Cat as a sacrifice to the fickle gods of M$ Windows. Sorry, I do not have a better idea.
Finding the sweet spot for placing naval reinforcements can be difficult at times and here the WW1G interface does us few favours. Make certain Hipper is in port and this is also an important consideration for receiving automatic ship replacements , like Lutzow and Hindenburg which join the Derfflinger unit upon completion but only if the Derfflinger unit is located in port when the reinforcements are due to arrive.
If you don't see the tool tip opening that shows the forces that are present in the port, don't release the mouse button. Hipper can command up to 6-BB/BC/B units so there should be no organic reason why you could not place the Derfflinger unit.