Why some times Answers are not shown after submit?

When I answer a question the answer is not shown after the submit or when I refresh a question page I can't see recent answers.

Looks like cache invalidation is not working properly for you.

I am guessing that this might be because your cache is not set up correctly and you are using a multiprocess setup for the application.

In the newer version of askbot some chunks of HTML and data are stored in cache and actively invalidated when certain things happen to questions/answers etc. Therefore with the default per-process cache of type "locmem" page renderings by the sibling process instances may not be the same.

Try using redis cache or memcached.