UK Radio switch for boiler seems dead

Hi, picture attached. I have UFH on ground floor and 1st floor, each with their own manifold and their own control box for the actuators. By chance I discovered that there were two live feeds into these control boxes: on from the 3-pin plug that sits beside them, and the other feeding back into it from the boiler. This was not noticeable until a plumber pulled out the 3 pin plug, only to discover that the pins were live as the boiler live feed was flowing into them (I guess only when the boiler was triggered by a timer as this back feed of live wasn’t permanent), and he got a belt of it. (Deadly!). Anyway, the solution was to replace the 3 pin plug with a radio controlled switch (done by electrician). This has worked fine, until the last couple of days when I notice that the switch upstairs is not coming on. You’ll see on the picture that the green light is on for the downstairs manifold (working) but red for upstairs, despite the controllers calling for heat. How can I test these radio switches / likely poor lens or fix. Would like to understand these better before I call the electrician back on for a chat.