Absolutely, its not emitter (pipe) failure in the most cases just circulation failure .
Undersoil invariably uses quite low temperature water in larger diameter pipework , basically meaning theres a lot of volume of water to shift around long loops of pipe , Remember its not heating just frost protection.
Its doubtful only one pump covers the entire system as it wouldn't make practical sense, a single pump failure covering part of the system or something as simple as a fuse or contact and nothings going to work on the affected section . Guess they found that when they got there this morning.
Just one of those things , guess we've all woken up to find the heatings not working at some time, even on a well serviced system , its not different.
I guess the pic below might give people some idea of what's below the pitch.
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