Your boiler has temporarily paused because the water leaving the unit is getting much hotter than the water returning, suggesting a circulation problem.

waiting time: temperature difference flow - return sensor too high (Check thermistor fit)

What causes this fault?

This fault occurs when the boiler detects that heat isn't being moved away from the unit quickly enough, causing the outgoing water to become significantly hotter than the returning water. The most common reasons are a failing internal pump that can't push the water around your radiators, or a buildup of sludge and debris that is restricting the flow within the system.