What is happening with this aborted flight?
It wasn't "circling around a built up area" - it was placed into a holding pattern.

At this point we can only speculate, but holding patterns are exactly as the name implies - aeroplanes obviously can't pull over and stop like a car can, so a holding pattern is a known position where they can just fly around without causing problems for other air traffic.

It could have been to sort something out on the ground, it could have been to give the pilots time to diagnose or work on the issue, it could have been giving time for the airport to handle the unexpected arrival.

It's next to impossible to guess - the only one I'd rule out is burning fuel as they look to have only done three patterns which is nowhere near enough to burn useful quantities of fuel.