I tried to add a split to The Dead Is Tired When the Morning Comes but only their part of the split was added, and twice.
(it's a split release with The Bottle Doom Lazy Band).
What happened?

Did you enter correct ID's for both bands? or maybe it's a bug?

Could it be that you add the ID of the first band in the box, instead of the second one? This would explain why this has happened.

I submitted it on the Bottle Doom... page and added the ID of the other band... strange.

If you provide the tracks for both bands, I can try to add it myself now

What is strange is that the other band page does not show your nickname on it, you surely made a mistake while adding the split.

I was able to add the split

I think you chose the wrong page to add the split, it looks like you added the split on The Dead Is Tired When the Morning Comes page and put the ID of this band, as it is the only band appearing.