When McMillan is breaking down the castle door, you can see hundreds of tiny holes that were drilled to weaken the wood.
When in the basement and Mac is getting ready to go upstairs and Enwright is going to stand watch, Mac calls him John, not Charlie or Enwright.
When Mac (in full kilted regalia) rides the mechanical "loch monster" to head off the villains, when he comes out, there is no sign of his ever having been wet.
After the death of Uncle Michael, there are heavy rains throughout the night. Yet the next day near the castle where the Highland Games are being prepared, there's no sign of mud or water anywhere which would be nearly impossible after heavy rains.