So, from a staffing point of view... Merlin are actually very short sighted. Their apprenticeship programmes are not very good. A place like Towers should be bringing in 1 or 2 engineering apprentices per year. The issue is that a £42k salary looks good to most of us, but the big issue is that a newly qualified engineer could go to the likes of Qatar for a couple of years and come back with enough money to buy a house. This means that there is a massive shortage in engineers in the country. Companies need to be growing their own, and creating enough supply to fill positions being vacated regularly.
Due to the types of people that apply for seasonal work (students) out of season workers are always a struggle for attractions to find - this is why they have staffing issues out with school holidays.
Galactica isn't broken. It has sensor issues which should have been resolved some time ago. The issue with Merlin and Capex projects is once the Capex is spent, there seems to be little money to resolve ongoing issues. You see it in a number of rides. Galactica bingo is annoying, and probably need the ride restraint sensor system to be completely replaced and reprogrammed. It is unlikely to happen... because the expense and it technically still works.
Thirteen needs the lift mechanism replaced. Again, it will be expensive but it is something that should be done. The downtime is horrific.
The issue with Towers is how many inherent issues that place has. Galactica, Thirteen, Hex, Skyride, Curse, the rapids, Spinball, Big Bob... they spend a lot of money on implementation, but skimp on snagging and PPM.