Well, since it’s an offically bugbased problem in RX 7 now I guess we’ll have to wait a while for it wo be fixed again.
In the meantime I transfer to RX 6 advanced, copy and paste to rx7 adv, do my work, copy and paste back to rx 6 and then back to Nuendo. 
It’s 2018 and I can’t see why I cannot just use drag and drop or double click to use external stuff like rx.
On my recent project for Amazon Prime I must have used RX a couple of hundred times…thank god RX6 still works…