While it is possible that there is an as-yet undiscovered error in a puzzle, it is highly unlikely. All of the puzzles in Geodyssey have been tested extensively by the constructor, by the test solvers, and by the many successful solvers of all three challenges.
If, while solving a puzzle, you encounter a contradiction or a situation that does not reconcile with the given information in the puzzle, chances are that you’ve made an error somewhere along the way. In that case, here’s my advice:
Start over from scratch, assuming nothing and being extremely judicious in making inferences.
Step away from the puzzle for a while, then come back to it later.
Clear your head by solving a completely different type of puzzle.
If you’ve done all those things and still are firmly convinced there’s an error, please let me know via the contact form on this site.