We often have a problem with reporting an issue to a wrong project.
You can clearly see reported project in the upper right, except it isn't true.
If, for example I browse to another project in another tab and then finish reporting , issue gets reported to wrong project and has to be moved.
Approx 10% of our issues have this problem.
Steps:

• browse to a desired project, click Add issue
• reload other tab with another project
• submit issue
• the issue is now in a different project than before.

Confusing thing is that you can clearly see the current project in upper right.
We often have 5+ mantis tabs open with various issues in progress and jump from projects when taking calls.