Throughout the series, Stephen and Matilda are both referred to as "Majesty". English kings and queens did not use the title "Majesty" until the middle of the 16th century, nearly 400 years after the setting of this series
Prior Philip is referred to by several characters as 'Father', 'a Priest' and a character at one point goes to make Confession to him.
In actual fact Philip was a monk and never a priest, so should have been referred to as 'Brother' not 'Father'. Also, in Catholic ritual only priests can hear confessions. Monks cannot.
The goof item below may give away important plot points.
When William Hamleigh rapes Aliena, he gets his henchman to cut off the right ear of her brother Richard to make her comply. But at the beginning of the following episode Richard's right ear is intact again with no sign of injury.