Why were you drilling if it’s an existing hole?

It was not a freshly drilled hole. I would always use the same size bit as the anchor diameter so I remembered that. A 10mm anchor in a 12mm hole would also be very loose which is not the case here.

I just now drilled a bit more after realising that the anchor should probably be flush with the brick, not the 10mm of plaster layered on top of it.

You’re using a masonry bit with a hammer setting right?

Yeah, and in fact it’s not just a hand drill with a hammer setting but a proper hammer drill with a shock absorber, a grease reservoir, and STS mounted bits (or whatever they are called). Before I bought the big gear I used a standard drill with hammer setting on poured concrete and it melted one of my bits because it had a weak hammer and spun fast enough to make the bit molten red hot.

I wouldn’t re-use this thing. This is the cheap type that comes free with things that need to be fixed to a wall.

Maybe too late to change now but I might consider a different anchor if it fails to hold my bicycle. I ended up drilling 10mm deeper so that I could push the anchor to be flush with the brick (thus 10mm recessed below the plaster layer). I also added a metal shard about the size of a toothpick between the anchor and brick. It’s holding for now but does not feel rock-solid.