It is not so easy to determine an apterous female even when you have it in your hand, it would be important to know the plants that surround the area of the find, for O. fagata the presence of Beech or Birch is almost essential, O. brumata adapts to many more plants especially Prunus.
From what I know, the females of O. fagata should have more developed wings while those of O. fagata a little less but both have anyway a very evident dark line on the wings.
The possibility remains that it is Agriopsis bajaria which has very reduced wings without evident dark spots, another species that flies in your country that has the apterous females is the Lignyoptera fumidaria.
Opteroptera and Agriopsis are in my experience linked to wooded areas, while Lignyoptera to steppe regions.
I am not aware of other autumnal species with apterous females, all the others are spring.
I hope to be proved helpful.
Ciao Lucio