Shower Pump comes on by itself for a few seconds - short cycling

I've a Grundfos STN-3.0 B pump in the apartment beside the hot water tank.
It periodically comes on by itself a a couple of seconds. Sometimes, it happens every 5 minutes which is very annoying. It has to be switched off at night to allow sleep.

It's a good few years old, I believe 7.

Anyway I've done a fair bit trying to rule out any leaks anywhere. None can be found anywhere except one which I'll get back to as it's not part of the pump circuit.

What I've done so far is:
Closed off incoming connections and then opened up hot and cold taps/shower to drain all the water out then open up again and switch on pump. When I do this, it usually increases the intervals, often there's no short cycling for hours but as soon as taps start to get use and water flows, the the intervals get shorter until eventually it can be every few minutes.


**That's an older photo, the damp concrete is from taking off the accumulator tank, it's perfectly dry now**

At one stage, I took off smaller, hot water accumulator tank and drained it of water. When I pump air into it using a bike pump, water sprays out through the threaded end. Would that indicate the bladder is compromised and it should be replaced?
To add to that, when I try to pump air into the tank when full of water, the pump doesn't seem to push down so no air seems to go in.

The larger cold water accumulator tank at the back is fair inaccessible so I haven't taken that one off yet.

One other thing, if I close off the outgoing pipes from the pump, the pump still short cycles so to me that indicates the issue is not a leak from a tap or cistern that's just not visible.

My options as I see them(in no order) are.
-Buy a whole new pump as that comes with all the bits that might have failed.
-Buy the bits that might have failed like accumulator tanks, NVR, pressure sensor etc and hope they resolve it. Looks like that's about half the cost of a whole pump.
-Disconnect the pump, take all the bits off and try to clean them, perhaps soaking in citric acid solution to remove limescale.

My only other option is to get a pro out but the issue I have is simply that I have never found a reliable plumber. Every time I've had a plumber out, they've said whatever job is probably going to be very expensive and then never get back to me with a quote. I always figure it out and fix myself then.
If I knew for certain the issue was with the pump, I could get a pump expert out to fix if needed.

I did once have to get a pump expert out to repair the pump itself as it stopped working. PCB board failed.
The short cycling was a minor occurrence before that but it seems to be worse these days than ever before.

Now, just back to the leak. There is a miniscule leak from one of the pipes from the water tank leading to what I'm pretty sure is radiators/heating system.
By miniscule I mean a single drop an hour or so from one of the threaded nuts. Sometimes nothing happens at all. It dries up before it even has a chance to drip again. I've tightened as much as I can so I suspect I'll need to disconnect, clean it and use plumbers tape or else just replace the connection that's leaking.
It's not part of the pumps water circuit but is there any chance that this could still be the cause? Would a tiny drop in water pressure from the main water tank cause a pump to short cycle?

Does any of that make sense?