I cannot say it with 100% surety but it could be installation error too. I am not sure. I have seen such issues long back. I re-installed the server and it worked for me. But since this is not your local server you are talking about may be you can try raising a service ticket with Adobe . 

@shikhasoni1 Your WF model actually gets created under /conf, but if it creates a structure under /var which is also required (sync) else your model will not be editable when it is deployed . Ref :- https://experienceleague.adobe.com/docs/experience-manager-64/developing/extending-aem/extending-work...

@desaiapoorva  Is it happening on certain pages or it is across the sites ? If it is happening on certain pages only , it would be issue with components.

This looks like a very common issue. It happens with me most of the time. 

Hi @Arindam15      Could you check https://hashimkhan.in/aem-adobecq5-code-templates/query-builder/ . You have pretty much everything you are looking for in here. Even though the blog is pretty old, all the content is valid unless there is any deprecated API , which is not there for query builder AF...

@Anmol_Bhardwaj Is this issue on Cloud ? 

There is no OOTB feature for that. But you can check the solution suggested by @Bhuwan_B 

Just an update on this one. On the same line we found out few issues with core components for cloud and has raised bug with the Engineering team.  Another issue we found out is missing Tab titles, when there is only one Tab. 

The portal looks great and well organized. Will explore more and give more feedback 

@srinivas_chann1 I also think the solution provided by @Nitin_laad is the right one. You can write an AJAX call on the selection change of the first dropdown and it should populate the second dropdown.