App reports the system is offline but there are no gaps in the climate curves

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On several occasions now I have been away from home and the app has reported that all rooms are offline, sometimes that resolves itself but other not and as a result we are unable to re-start the normal heating schedule before we return home. What I find curious is that once I get back online (and sometimes that happens with no intervention from me) there is no gap in the data in the climate/temperature curves for any of the rooms. I think that this suggests that the system did not go offline (or else how could it have reported the climate data) but that the app for some reason thought it was.

Anyone had anything similar, or have any suggestions?