Created primary index seems ok, but can't find any documents (after some time)

I use CB version 4.5.0 EE (build 2601) on my PC (windows 7).

I created primary index on bucket to be able to use N1QL and it worked as it’s supposed to for many days.

Today all my queries returned empty arrays. I checked the index, it was “Ready”, “initial build progress 100%”, nothing seemed wrong, only in “Query” bookmark when I clicked on my bucket in the list with “Fully Queryable Buckets” it said “No documents found, unable to infer schema”.

I had to remove the old primary index, create new and now it’s working again. All queries my app performs are SELECTs (I don’t add, remove, nor edit the documents), so I have no idea how could the problem with primary index arise.

This is actually second time it happened so I suppose that after some time, it’ll happen again if I don’t find the problem. Any advice?