Search result unreliable version 8.1.1

[citybillykid]

When searching in "Notes", search result is unreliable. By using same search criteria, sometimes search result is correct, sometimes "No items to show".

Environment:
Ubuntu 18.04.1 LTS 64bit
Java 1.8.0_201
MySQL 5.7.25
Logicaldoc-CE 8.1.1

How to reproduce:

1. Add documents and check "Immediate indexing"
2. Add new Notes "keyword" for the documents
3. In Full-text Search, run search with criteria below
   Expression: keyword
   Search in: Notes
4. Run search by clicking the magifying glass after "Expression" .

Result:
Sometimes return 1 result (as expectation)
Sometimes return 0 result.