The S. oxyacanthella group is notoriously difficult, and usually combination of characters of moth and genitalia give the best results, but this is one of the easier species: certainly Stigmella minusculella. The moth should be uniform greyish, with variable head colour, no androconials.
The valva without a lobe at the inner caudal margin is characteristic in combination with the shapes of gnathos, uncus and phallus.
Axel Hausmann (Author of the Geometrid Moths of Europe) says: There are no constant and significant differential
features in male genitalia between Epirrhoe alternata (Common Carpet) and E. rivata (Wood Carpet). However, the different external appearance (wing pattern) is correlated with differences in the DNA barcode.