"In the library the teacher writes inscriptions in German."
Translation:In bibliotheca magistra inscriptiones germanice scribit.
Duolingo's corrction algorithm is not case-sensitive. Additionally, Latin did not use capital and small the way we do. The fact that the volunteer course contributors have been using mixed case at all is slightly controversial.
Each individual prompt has its own database of acceptable answers that the volunteer course contributors maintain manually. There are bound to be inconsistencies between them.
I have no idea what the algorithm is for populating the word banks.