Raid not clearing or continuing after killing final raider in nether

I have a raid farm that I built off of a tutorial on YouTube. When I was repairing the farm, a raid spawned in with on the the Ravengers. The avenger got out and went into the nether. When I killed him there, it would not resent the raid. It took logging in and out many times before it would clear. 

 

I use the Minecraft android version on a Mac.