Underfloor goes off - stays off

[BubzyT]

Hi. Really strange one. Our underfloor works lovely. But once it clicks off, it stays off, resolutely. This can be either from the zone thermostat or, strangely, after we've showered using water for a megaflow tank. It's speedfit manifold but I think problem might be with JG wiring centre. No signal is being sent.

After about 6 hours the system clicks back in again, all by itself, and the underfloor starts up.

Underfloor system set to permanently on (controlled by thermostats)

Anyone seen this problem before?