Nur Azlina,
The forum is not the right place to submit bug reports. You should be doing that in the bug tracker (https://openacs.org/bugtracker/openacs/) as indicated in dotLRN's project page (https://openacs.org/projects/dotlrn/).
You can also submit patches to fix the bugs you (or others) have submitted, and that practice is highly appreciated and regarded.
The forum is for discussion and questions.
-Roberto