Hot water getting stuck on
I've been using Tado for several years, and have recently noticed that my hot water is getting stuck on (for hours/days) despite it showing as "Off" in Tado.
I have a regular ("heat-only") boiler, unvented hot water cylinder, Tado Smart Thermostat, Tado Wireless Receiver (Extension Kit) and Tado TRVs.
It's an intermittent issue, and turning the heating system off and then back on at the mains seemed to temporarily resolve it, but then it would get stuck on again a few days later.
I initially thought it could be the relay in the Extension Kit getting stuck, so I got a replacement (Wireless Receiver) but this hasn't solved the issue.
I have temperature sensors in my hot water cylinder and on the flow and return pipes, so I can easily see when the cylinder is being heated when it shouldn't be.
I've asked Tado support, but they're not being very helpful, talking about other smart devices and bridge placement. But as the hot water light on the Wireless Receiver is off, when the cylinder is heating, it surely can't be a Tado wireless issue.
So is this almost certainly a fault with my boiler (5 years old)? Or could a fault with another Tado device be causing this?