Hi Bronius,
Thanks for contacting Syncfusion support.
We checked in our sample by defining enablePersistence as true and filtering operation has been working fine in our end. In persistence as true state, data persisted in correct way after page refresh. So, please share below details to validate your issue.
1. Explain below case briefly - Filtering is not working : Facing this issue in any specific integer/string type column or entire grid column?
2. Syncfusion Package version.
3. Facing this issue in any specific browser.
4. Please explain your issue reproducing steps .
5. Pictorial representation/ video demonstration of your issue.
Regards,
Prasanna Kumar N.S.V