Random not expiring & posting issues

We can’t figure out a rule, why sometimes randomly posts are not expiring or being posted by the plugin. Could you please propose a solution or a testing method to eliminate these random issues?
We are pretty sure that we don’t have a user input problem. We use the current WP system and plugins. Our issue rate is less than 3% with about 50 posts per month – but these hurt sometimes. Our provider seams to work correctly. Randomly turning off other plugins isn’t an option, because we use them all on a running system. Maybe there are certain other plugins to watch for, because of known issues? Maybe we should use a supporting plugin?

Thanks for your great Post Expirator plugin!