This is a pretty lousy one, but on the second tape, Bill is talking about how Stan was the last one to see Penny-wise that summer,and he says something like "Stan was in the park near the bird feeder..." When it cuts to the childhood Stan, he is near a bird BATH....
First of all, they were kids when it happened so since 27 years had passed from the time of the incident to the time of the relating of the story it's pretty easy to understand how a few insignificant details would be wrong. Secondly, Bill is telling a story that didn't even happen to him, so maybe he didn't know the exact details.