Hi Tullio,
We hope that you will be satisfied with our components.I guess by trial version you use the community version which will have the watermark showing up except for our free components such as Table, Tree, Tabs, Menu
However we have tested the combobox with the code that you provided us and looking at the function I can suggest that mostraAlertMsgOption(this); eseguiRefresh(this); functions are invoking an alert message and a page reload. After some testing I encountered your problem in Firefox and the problem was coming from the selected attribute from the list item which is a native HTML attribute.Solution for fixing this is to use selectedIndexes or selectedValues property of the combobox.A quick example on how to do this :
 `<smart-combo-box id=”combobox” name=”e818843742″                     
drop-down-position=”bottom”                     
selected-indexes='[1]’  
                   onchange = “mostraAlertMsgOption();reloadFunction();”>        
<smart-list-item value=”LAN” >Lang</smart-list-item>       
 <smart-list-item value=”LAN2″ >Lang2</smart-list-item>    
</smart-combo-box>`
If you prefer to use selctedValues just replace the selected-indexes with selected-values= '["LAN"]'.
Please, do not hesitate to contact us if you have any additional questions.
Best regards,
Yavor Dashev
Smart UI Team
https://www.htmlelements.com/