Search API - empty results

I'm using Search API to fetch a list of tickets.
Then I delete the first 100 tickets via the API (destroy_many).

When performing a search query again. I get a list of empty results as the first page, while the "count" property of the response indicates there is still data available for the search.

1) Is this due to indexing & the fact that tickets have been deleted recently?

2) The deletion job cannot always process all tickets. E.g. "total" = 100, "progress" = 78, "status" = completed. Is this a problem / what can be the cause?