A new garden species: Sciocoris cursitans [1,2] (Confirmation identification GerardL). The small insect roamed the stacked walls in the garden.
It’s round shape and large scutellum are striking, although the small size make it rather easy to overlook.

There is another bug species from the same genus present in the Netherlands but that one is mainly seen in the most southern province. One of the differences between the two is the presence of a notch just above the eye, which in S. cursitans is small or not present.
References
1 Nederlands Soortenregister2 Aukema, B., Th. Heijerman & V.J. Kalkman 2016. Veldgids wantsen deel 1. – EIS Kennis centrum Insecten, Leiden.