Repair or Replace Pressure Pump

We’re having issues with our Stuart Turner pump. It’s constantly cycling (running for a few seconds every 10 seconds) or it won't start at all. We’ve had to keep it switched off and only turn it on when we need it. Even then, we usually have to reset it multiple times before it actually kicks in. To rule out a leak in the taps or pipework, we isolated the pump by closing all the outlet valves, but the problem persists. Since it’s still cycling even when isolated, it’s unlikely to be a external leak in my opinion.