Different result searches, not correct behavior

Making different searches, using different criteria and indexes, I'll notice the following:

1. Sometimes the application doesn't show all records: I see 8 of 13 records or 210 of 221 records. It's not possible to go ahead with the scroll ball

2. Sometimes to make active the scroll ball, I need to select the last record of the list. In this way the scroll ball become active and I will able to see the other records.

3. Sometimes the result list show more record that the total result: for example 99 of 57 bibliographic records.

Please, see the attach.