[Search API] Searching doesn't work at all. Shows non accurate search results.

Hi,

I have a site where I use Search API.
The problems are:
- searching for phrase "d&o" doesn't work:
- normal search won't show anything on first result page
- searching for "d&o" gives proper results
- using html filter preprocess - doesn't change anything
- searching for phrase "ubezpieczenia oc" doesn't work:
- there is a page with such title, it doesn't show in search results or shows near the end
- setting full text for only title doesn't change anything

Search Views is set:
- Operator: Contains all of these words
- Parse mode: Single Phrase