Thanks, Loki, you have identified my problem, at least!
I would have to disagree about the desirability of leaving the RRU's with AGN, though. They spend their time repairing useless breaks in Kurland, for example.
But your comment about the desirability of leavng the RRUs with AGN has raised another question for me. Is there any weight given to where supplies are needed in determining where an HQ should send the RRUs? In my current game, I am using the AI assist to do things I don't want to bother with, like deploying air units from reserves and moving AOGs forward as the battle moves on. But one choice the AI made for moving the AOGs was to send several of them to Kurland, which is certainly closer to the front, but is otherwise off the beaten track. On the one hand, it is good to have the AOGs there, because they can draw supplies from sea transport and not overload the slender RR thread leading further north. On the other hand, AGN has decided that the RRUs can best be used repairing the RR network serving those air bases in Kurland. That really limits how efficienctly I can spread the rail net eastwards towards Pskov, among other place, and by turn 9 or 10 those limits are pretty devastating.