mdbox Inconsistency in map index

[bOnK]

After a (power)crash two accounts have been corrupted.
I tried to rescue things by running force-resync multiple times, but 
that didn't work out.
Searching the archives, I found a recent suggestion (by Timo) to delete 
the index files, but I'm not sure which files to delete and what the 
consequences will be.
When I deleted ``storage/dovecot.map.index'' in an unimportant account 
of my own, things only grew worse and I decided to delete the account 
and start fresh...

Something I obviously don't want to do with the other account as it 
belongs to a client with about 2.5G mails (856 m.* files), which we 
don't want to lose.

I have observed the following behavior in the logs:
When a new mail arrives:
(The second line below is always the same, however there's no mail with 
uid 12819 according to doveadm search uid 12819)
Mar 04 11:43:28 lda(user): Warning: mdbox /var/mail/user/storage: 
Inconsistency in map index (117,1060 != 117,1883660)
Mar 04 11:43:28 lda(user): Error: Log synchronization error at 
seq=117,offset=1546660 for /var/mail/user/storage/dovecot.map.index: 
Extension record inc drops number below zero (uid=12819, diff=-1, orig=0)
Mar 04 11:43:28 lda(user): Warning: fscking index file 
/var/mail/user/storage/dovecot.map.index
Mar 04 11:43:28 lda(user): Info: 
msgid=<d760229d563e99dc787acd0746b18b31 at feedback.1dayfly.net>: saved 
mail to INBOX
Mar 04 11:43:28 lda(user): Warning: mdbox /var/mail/user/storage: 
Inconsistency in map index (117,1060 != 117,1883784)
Mar 04 11:43:28 lda(user): Warning: fscking index file 
/var/mail/user/storage/dovecot.map.index
Mar 04 11:43:28 lda(user): Warning: mdbox /var/mail/user/storage: 
rebuilding indexes
Mar 04 11:43:28 lda(user): Warning: fscking index file 
/var/mail/user/storage/dovecot.map.index
Mar 04 11:43:28 imap(user): Error: 
/var/mail/user/mailboxes/INBOX/dbox-Mails/dovecot.index reset, view is 
now inconsistent
Mar 04 11:43:28 imap(user): Info: IMAP session state is inconsistent, 
please relogin. in=2011 out=108358 deleted=0 expunged=0 trashed=0

When user logs in next (might be from another box/MUA)
Mar 04 11:44:36 imap-login: Info: Login: user=<user>, method=PLAIN, 
rip=82.95.XX.XX, lip=37.97.XX.XX, mpid=14884, TLS, 
session=<VfvML+ZJuO9SX18R>
Mar 04 11:44:37 imap(user): Warning: mdbox /var/mail/user/storage: 
Inconsistency in map index (117,1060 != 117,1884336)
Mar 04 11:44:37 imap(user): Warning: fscking index file 
/var/mail/user/storage/dovecot.map.index
Mar 04 11:44:37 imap(user): Warning: mdbox /var/mail/user/storage: 
rebuilding indexes
Mar 04 11:44:37 imap(user): Error: 
/var/mail/user/mailboxes/INBOX/dbox-Mails/dovecot.index reset, view is 
now inconsistent
Mar 04 11:44:37 imap(user): Info: IMAP session state is inconsistent, 
please relogin. in=331 out=178391 deleted=0 expunged=0 trashed=0
Mar 04 11:44:37 imap(user): Warning: mdbox /var/mail/user/storage: 
Inconsistency in map index (117,1060 != 117,1884396)
Mar 04 11:44:37 imap(user): Warning: fscking index file 
/var/mail/user/storage/dovecot.map.index
Mar 04 11:44:37 imap(user): Warning: fscking index file 
/var/mail/user/storage/dovecot.map.index
Mar 04 11:44:37 imap-login: Info: Login: user=<user>, method=PLAIN, 
rip=82.95.XX.XX, lip=37.97.XX.XX, mpid=14886, TLS, 
session=<AUTbL+ZJuu9SX18R>

Besides the nuisance of getting kicked of every time a new mail arrives, 
user cannot delete mails (as in: move to Trash).

TL;DR: which files to delete and what will be the consequences?

-- 
b.