When you create a title for a TV series, the credits are added to the series page. When you add credits to individual episodes, you have the option to quickly add credits from (I think) either the series, a season or another episode. However, the credits available from the series level are the same credits that were added when the series was created, meaning they are often vastly incomplete and incorrect (because they've been fixed up for individual episodes but not the series due to the restrictions on editing series credits).
I've read that the credits added at the episode level are supposed to replace the ones added at series level. It's true that when you look at the entire series credits, they are (mostly) the credits rolled up from the episode credits. However, the original series credits are still there in the editing screen if you edit the credits for the series. It's not possible to change these credits as IMDb only wants you to edit credits for individual episodes. So if the series credits are supposed to be replaced, it's not happening, or if it is, it's taking an extremely long time (I'm not talking just days).
One specific problem that I've noticed this is causing is what's happening with this actress (http://www.imdb.com/name/nm2652475/) for example. For the series UnPhiltered, her credit was originally added incorrectly as an acting credit under her (stage) name, Grazia Nelson. For the one episode she was in, the credit was then added correctly as a self credit. On the page for UnPhiltered, it appears correctly. However, on her page, it's appearing as two separate credits - one with the correct self credit and one with the supposedly replaced acting credit. This situation is likely only caused when the series credit and episode credit differ between acting and self. However, it clearly shows that the old series credits are not disappearing.
I think it would be better if all the rolled up episode credits that you can see on a series page were editable from the series page. This would allow users to add credits to multiple episodes at once and correct an incorrect credit that's been attached to multiple episodes.
I've read that the credits added at the episode level are supposed to replace the ones added at series level. It's true that when you look at the entire series credits, they are (mostly) the credits rolled up from the episode credits. However, the original series credits are still there in the editing screen if you edit the credits for the series. It's not possible to change these credits as IMDb only wants you to edit credits for individual episodes. So if the series credits are supposed to be replaced, it's not happening, or if it is, it's taking an extremely long time (I'm not talking just days).
One specific problem that I've noticed this is causing is what's happening with this actress (http://www.imdb.com/name/nm2652475/) for example. For the series UnPhiltered, her credit was originally added incorrectly as an acting credit under her (stage) name, Grazia Nelson. For the one episode she was in, the credit was then added correctly as a self credit. On the page for UnPhiltered, it appears correctly. However, on her page, it's appearing as two separate credits - one with the correct self credit and one with the supposedly replaced acting credit. This situation is likely only caused when the series credit and episode credit differ between acting and self. However, it clearly shows that the old series credits are not disappearing.
I think it would be better if all the rolled up episode credits that you can see on a series page were editable from the series page. This would allow users to add credits to multiple episodes at once and correct an incorrect credit that's been attached to multiple episodes.



Matt
Even if that is supposed to be true, it isn't working consistently, even for credits that are identical.
DavidAH_Ca, Champion
I also noted that the removal seemed inconsistent, sometimes appearing to require several Episode credits, sometimes only one. However, it may be that the routine that removes the Series credits in only run occasionally (like the one that updated the Title year from the Release date) and that several Episode credits were added between runs. I am fairly certain that the routine does not run daily, but I have no idea how often it is does.