The sewage system is basically overworked because of the amount of toilets in each carriage. Before obviously it was just one set in each carriage and 3 in the "accessible" one because of accessible toilet. Because of the multiple toilets now for the berths with en suites, at some points the staff have had to reshuffle passengers to another berth a few times because the sewage system has been overloaded, and a "sloshing noise" can sometime be heard when they train has been particularly rocky. A few times the blue sewage water has been leaking literally into the berths because of the overflow issue h,moving passengers. Apparently it's been found out the reason for this is because they have been essentially using plastic (or some similar material) piping, and obviously with the sewage chemicals, it's been burning away at the plastic and hence the leakage, because that piping is trying to support sewage/chemical water from multiple toilets.
Berths have an intercom type system so passengers can call (like room service). However they found a few times when the Edinburgh and Glasgow trains get attached together, the wiring connection meant when passengers for example are in the berths going to Edinburgh and try to use it, it has then connected to the staff on the Glasgow part of the train and visa versa, meaning at times obviously they can't be relied on.
The old trains apparently have a covering underneath to prevent things like snow/mud/branches etc being kicked into undercarriage. However the new trains don't have this, and therefore when they trains are running to Fort William, because of the type of terrain, problems start occurring with the train when travelling through that area meaning train delays and having to get engineers clearing out undercarriage all the time. Millions has been poured into the new trains and already these things are happening and causing more havoc for staff.