Ever since the 1.7 update it seems there is a bug with commisioning a crown artifact where it always results in the lowest quality artifact despite any modifiers.
I have commissioned around 30+ crowns across 3 games, using high aptitude antiquarians, maxed out court lodgings and successfully hitting every opportunity to improve a crown's quality and yet I haven't received a single crown that wasn't the lowest quality "fine".
Other artifacts seem to be fine, I have high quality artifacts of every other type that I have commissioned.