I fixed the problem after some more tinkering.
I had two problems:
1. I called updatebounddata on the second grid before initializing it. ocistiGridIMeni(); this was the culprit.
2. I didn’t use filter-items=”true” in the HTML <jqx-grid-column datafield="sklId" min-width="285" filter-type="list" editable="false" text="Šifra"></jqx-grid-column>
