I've seen this live action movie as a child in late 1980s or early 1990s on a black & white TV in Hungary with Hungarian voices (probably dubbed). It has stayed with me a long time now, but I still haven't figured out what it was. I remember a number of details, but I'm not sure I remember everything right.
The story starts in a Christmas festival. A brother (around 6) and sister (around 10) have a look around and end up in Santa's trailer. He tells them a nursery rhyme (that actually rhymes in Hungarian): "Close your eyes and open your mouths, I'll give you some candy." They do as instructed.
When the sister opens her eyes she got no candy and also her brother and the guy dressed as Santa are gone. She's alone.
She goes looking for the brother. It takes years and she has many adventures. One I recall is a visit to a village that turns out to be built on the back of a huge dragon. (Maybe drilling a well disturbs the dragon's slumber.)
She ages. At some point an inventor joins her on the quest to find her brother. The inventor helps her get to her destination, a castle in a forest. At the end he builds a Leonardo da Vinci-style flying machine to get past some obstacle (orcs?). The inventor perishes though and his book of inventions with him.
She makes it to the castle though. Her brother lives there as the prince. He does not quite remember her and seems a bit cold. But then he starts sketching a flying machine, just like the inventor did! I'm not sure exactly what that means, but yay!