You're doing nothing wrong and the app is doing what it is supposed to do
Just keep pressing enter, it will eventually stop. You must have a TON of saved games on your computer. I say this because the app is going to EVERY save game (and all the files it needs to modify for that save game) and updating captain's name in it/them. There's like 7-8 files for every save game it has to update.
It will do the exact same thing for the u-boat hull number