Logs normally show causes for the failures, look in the background method server log for details. The queue manager may show some exception traces as well. The custom code is always a potential problem, you should <u>always</u> write the code in external classes and call it from within the workflow. The code should be wrapped in atry..catch and be especially careful putting code into conditionals these have some weaknesses especially with transaction handling, we normally write the code to execute in a block before the conditional and set a variable. As far a I know the workflow engine has not fundamentally changed fora while so the cause of your problems are more likely to be environmental, missing classes, soft types etc.
Ideally all developers should develop workflow code in external classes, with compehensive junit testing.
