I sort my message list by message number in most-recent-first order (i.e. # field with triangle pointed up).  If I have no more unread messages in my inbox and I hit N to go to the next unread message, Claws will put up a pop up that says:

Process mark

Some marks are left.  Process them?
[ No ] [ Yes ] [ Cancel ]

I hit yes to process all my pending move and deleted messages.  Claws leaves me in the next folder I'm subscribed to with an unread message.

This is all fine so far and expected.

However, if I now go back to the Inbox, some times the sort order is lost.  Basically, the triangle goes away on the # field.  It doesn't happen all the time, but if it happens, it's *only* after N-ing to another folder.