This boat has 2 tubes forward and 2 on the back. After firing the first forward the 2. tube is not switched active automatically and can’t be activated manually either. Only when the first one is reloaded one can launch the torpedo and after this the 2.forward tube can be used, the same with the back tubes. I observed this in naval arcade - didn’t test it with realistic battles.
addition, the torpedo launch at all ships/boats (not only german) with spare torpedos is bugged - one can’t switch to another tube if the first one is expanded and not yet reloaded. This is very annoying and limits the combat value - but hey we have a new update…