Its likely the crank is 1 tooth out, looking at those. Probably previously fitted by somebody who thought they could do it without a locking kit.
Ok, the engine seems to run fine. But using the locking kit I've got I will correct the issue.
Is this common with people who try not to use the locking kits then?
Yes. The timing tools are often misunderstood; the locks are to save you needing extra hands, but the gauge and crank tool are actually the heart of the set.
The other cause is not turning the engine through enough times. With 5 toothed pulleys, up to 3 adjustable rollers, and long belt runs there are lots of potential causes of the timing being wrong. Mine was a tooth out on all four cams, and had extra Tippex marks which is a sure sign of not using the timing tools. Having said that, I do like to highlight the original marks.