combo in a tabbar

Are they any limitations in we using combo in tabbar? We used a tabbar and wrote code accordingly so that there are a couple of comb boxes in our 3rd tab ( not the default tab). When we navigate to this tab we see the combo controls are in disabled mode. Using the readonly property also did not change this behavior

Can you share a peace of code ( snippet or demo link ) where problem can be checked ?

There are no limitations on using combo in tabbar.