Started having issues with the K9 mail app about 2 months ago on my Droid Inc. Recently upgraded to a RAZR Maxx, reinstalled the app, worked fine for about a week then started having the same issues that I was on the Incredible.
-messages already read going unread again when mail is checked
-not syncing properly (i.e - sent email from phone does not show up in "sent items" when checking mail later on PC)
-seeing UID COPY 531,530,5 on all email folders after checking mail/syncing
Also on the Incredible I had some force close issues as well, that has not yet repeated on the Maxx though. I did not change any settinges so not sure what the problem is. K9 last update seems to be in February. Just wondering if anyone else having similar issues.