CM
I assume you're referring to this.
Migrant crisis: Navy rescue ship HMS Bulwark breaks down due to too many migrants | UK | News | Daily Express
Aside from the fact that "stuff" breaks down from time to time, it may just be that supporting hundreds/thousands of people who are basically being transported on the upper deck and hence likely to need more frequent supplies of drinking water has put the margin beyond what one would normally tolerate - particularly towards the end of a deployment.
Hardly the RNs "mess".