IT Services shows incorrect SLA values.

Many services were affected for 4-5 or max 10 minutes, but the SLA still counting that the service is down since many days (some 2d some 4d some 6d).
This problem still until I remove and add those services again on frontend, something is wrong with Zabbix so please check it, IT Services are very important feature for zabbix.
If you need anymore info or screenshots then please let me know.