This ticket doesn't provide steps to reproduce the issue. Is Contributing Bug Reports unclear on this matter? Can we provide better documentation somehow?

Specifically, we need full steps to reproduce the issue. These need to be, from start to finish, full steps any engineer either one day or one year from now can follow and achieve the same error:
https://secure.phabricator.com/book/phabcontrib/article/bug_reports/#include-reproduction-ste

If your item is not easily reproduced, or requires very unique environmental circumstances to reproduce, we may not ever be able to reproduce it. See:
https://secure.phabricator.com/book/phabcontrib/article/bug_reports/#unreproducible-problems

I have updated the phabricator tio recent version on Dec 2.

You can reproduce the issue using following steps,

• Upgraded the phabricator search features to elasticsearch.
• Go to Diffusion >> Active Repositories
• Then chose a repository, click on a commit and then select "Edit Maniphest Tasks" then a popup window will open as "Manage Attached Tasks" it shows "Loading..." but not showing any tasks.

Upgraded the phabricator search features to elasticsearch.

We need more details here.

Unfortunately, given the lack of reproducible instructions and no other reports, there isn't anything currently for the upstream to do on this ticket except to ask whoever is having it, to provide us with more details. If we can't reproduce something, there isn't really much more we can do. The onus is on you to help with that effort.

Upgraded the phabricator search to elastic search using the following command.

./bin/config set search.elastic.host 'http://localhost:9200'
./bin/search index --all

Which is working fine when reverted back to default search option.

A quick update here, as per our analysis we came to know that the current issue was arised due to the elastic search related issue and we have fixed it. Now everything is working fine. :-)

So thanks for your support and assistance.