When a raider travels through a nether portal, it does not get removed from the "Raiders left" bar, and the raid will not continue even when it is killed in the Nether and instead stay in a incompletable state.
Linked issues
is duplicated by 2
Comments 3
I've reopened this bug report, since MC-140113 was fixed before this was reported, and as such the issue reappeared after it was fixed previously.
I'd like to report that this is not the case in snapshot 20w09a. When the pillagers entered the neither portal it counted as a kill and lowered the raid bar. I took out all three waves this way and got a victory for it.