Normal
I think this is due to how the anime industry operates. Since a lot of anime is based on the manga but often the manga is incomplete when the TV series is being made so the anime production team just has to wing it. OVAs are better because they're made specifically to follow the manga. But then that's how you get into the mess of needing to keep track of different timelines when the original TV series has already been made. Some examples I can think of are FMA vs FMA: Brotherhood and their side movies, Hellsing (both timelines sharing the same name), Code Geass R2 vs Re;surrection.