If you are using Azure with auto-scaling and you are using the builtin Episerver Search (not Find), search results will likely be corrupted at some point.
This is based on the below blog post which stated the following.
"Can I use Search, the built-in search function in Episerver CMS, instead of Find?
Viktor: I wouldn't recommend it. A key value of the DXC Service is its automatic-scalability. Search is file-based, and gets corrupted when the DXC Service scales and the index file is copied to a new machine."
Use an alternative search provider such as Microsoft's Azure Search or Episerver Find.