MK2.5 2.0pd injector issues

Morning all,

Getting really frustrated with some injector issues on my Octavia, and wondering if anyone has any suggestions/thoughts?

'09 facelift MK2 2.0pd 140 BKD engine code on 160k miles. 

Back in March the car started running really rough (felt like running on 3 cylinders), but only periodically, sometimes turning it off and on again would stop the rough running and it'd be fine for a while. When running rough it had no power and was shuddering. Garage diagnosed and fitted a new injector loom, seemed to fix the issue. 

Car was then SORNed while I worked from home over lockdown. Put it back on the road at the start of Sep. Did 300 trouble free miles, car running normally. Then the same issue started again. Basic OBD scanner showed P0202 error code, problem with injector/circuit on cylinder 2. New injector was quoted the best part of £600, so found a supposedly tested second hand one and had that fitted. Ran fine for 5 miles then same issue began again, that's where I am now, still with the P0202 code present. Any thoughts on the likely issue would be appreciated.

- New loom was a dud?

- Second hand injector was a dud?

- Some other issue that the basic OBD reader isn't showing? 

Cheers.