could it be worm casts,?

Fill the hole in and see if your camera catches anything digging itself out. If the hole stays filled then you need wonder no more.

I have the same issue on my allotments... I moved the pile and put back in the raised bed ( i thought too big for worm casts), and the next time I went about 5 days later, a pile again in the same place. would be interested to see answers...

Moles? We have a mole hill with a hole in the middle, but not six inches across. I assumed it was where the cat had been trying to dig out the mole as she has done that before.

Saginaw, welcome to GoY. Thats a lovely statue by the way. That's my thought too Stera_g, moles. I have a similar issue at the back part of our lawn, near the hedge bordering with the farmers field. I have dug out a trough and sunk some old thick ceramic tiles into the ground to make a defence wall. This seems to have stopped the moles advances. Hopefully it has given up in my garden and gone back into the field .... Time will tell ...lol

if it was a creature that walked out it would have pushed the soil down and or kicked the soil everywear as its diggi9ng in but your animal seams too be digging out which seams like moles though id of thought bye the nature of moles there would be more mounds quit quickly as they are territorial so in a new place to make a new territory . they need a lot of tunnels to let worms drop threw and push the soil out every few yards . id do as said and fill the hole in and watch your camera .

Zogina, please accept my apology. In my comment above, the predictive text, made a change to your name. I didn't spot it in time to be able to edit it. <]:~))