You can check the mailbox data consistency by performing an omscan on your mailbox,use the steps below:
omoff -d0 omscan
omscan -Z
omon omscan
You need to watch the status of the omscan process using the command:
omscan -t
Wait until you get a message that says "Current server cycle not started; service reset or delayed".
Now try to fix the mailstore related issues in active mode using the below given command:
omscan -AvfxS -U <username>
Note: <username> should be the username for the user in question.