I have lots of filters to organize my copious incoming mail. Messages get moved into topical boxes. Recently I've noticed that a mailbox has unread messages in it and when I open it, I see the new messages for an instant and then they disappear. And another mailbox now has unread messages. So it seems that the filters run on the inbox when the mail is received and then they are run again (but a different set are applied) when I open the mailbox they got moved to by the first run. I see no settings in the Filters dialog that has anything to do with this behaviour. Why is this happening and how can I stop it?

BTW, most of my filters have Stop Execution as the last step. (Most only have a single Move to... action followed by Stop. And for performance reasons, all newly created filters should have Stop as an automatic 2nd step since most users wouldn't think to do this. )