The bell that is made and installed in the church by Tinker Jones in the episode "The Voice of Tinker Jones" is missing from all town scenes in the future 2-part episode "The Lord is My Shepherd".
When Tinker Jones and the children have put all the items gathered to be melted down, they are in a big overflowing pile. They need more items so the children run off to fetch more. In the panned away shot, everything has already melted down even though it was only put in seconds earlier.
From 26:26 - 26:29, as Mrs Kennedy leaves the room with her hands on her face, you can see she is wearing a modern bra.
When the children gather round to watch Tinker cast the bell, Willie is standing against the opening in which there is supposedly an open roaring fire.