Ive had this issue for about a year now. I am on Bedrock for iOS, updated to the current fix. I start raids and complete a few but on random waves it will cease playing the horn, and no pillagers spawn. The raid bar will be on a variety of fullness, for example, this case the bar was about 1/5 completed, but sometimes it is full purple. The issue will randomly fix itself after several days of logging off and on with no rhyme or reason for resolving. Thanks in advance, i truly love this game so much. <3