I do not do searches on sub fields of repeaters, in fact I go out of my way to not use repeaters when I have to use the data in searches.
When I must use a repeater for data that needs to be search then I find creative ways to not actually search the repeater. Here is a post I wrote years ago on the topic in the internet archive https://web.archive.org/web/20190814230622/https://acfextras.com/dont-query-repeaters/
Another way to that I have done something similar is the same way that “The Events Calendar” plugin manages repeating events. There is a hidden post that represents each event. When the main post is saved then hidden child posts are added and deleted as necessary. Searches are performed on the child posts, these are used to get the parent post.
