Bug Reporting

The number one cause of "bugs" in Pyfa is simply user error. You meant to fit the meta 5 instead of the meta 0. You forgot to update your skills. You forgot that there are fleet boosts being applied to the fit, or that you have a Wormhole effect projected. Please double check your fit, your skills, and anything that may affect these attributes. Also make sure that Pyfa is updated to the latest version.

Now that we have determined that what you're experiencing is indeed unexpected, please see below how to proceed:

Fit calculations

Please be as descriptive as possible. This is not descriptive:

The bonus of Heretic doesn't work

This is infinitely better:

Both Corax and Heretic can fit 7 Rocket. Corax (5% kinetic damage) fitted with Caldari Navy Scourge Rocket and one Ballistic Control System, it has 199 DPS. However, when Heretic (5% all damage) fitted with one Ballistic Control System, it just has 126.

Some useful troubleshooting can be performed by checking the Affected By tab in an items stats window. This will show you what skills / ship bonuses / modules are affecting that particular item. Posting the fit in question is a tremendous help as well. Screenshots of ingame stats vs Pyfa stats are awesome too! =)

Crashes

Sometimes Pyfa may crash. This is in response to something that happens in the code that Pyfa doesn't expect, so it chokes. Unfortunately, Pyfa's error reporting is a bare minimum. It may log it to a file, but a lot of times it just fails silently. This is something we hope to fix in a planned rewrite of Pyfa: better error handling, notifying user of exact error and trace stack, and better debugging tools for the developers.

If you find that Pyfa has crashed, please try to reproduce it and note the steps leading up to the crash. There might be some information in the error log, which is located by default in .pyfa in the users home directory.

Reporting

You can report bugs either in the Pyfa thread on the EVE Online forums, or on the Pyfa issue tracker on GitHub.