After [b]updating SOGo from 2.3.17-1 to 2.3.19-1[/b] (using the inverse repository [b]rhel6/CentOS6[/b]) some very old recurring events reappear (multiple time) for a few users

tables for one user affected by this problem:
[code]
SELECT TABLE_NAME
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME like '%mylittleponey%'
and TABLE_SCHEMA = 'sogo'

+-------------------------------+
| sogomylittleponey0012c48149e |
| sogomylittleponey0012c48149e_acl |
| sogomylittleponey0012c48149e_quick |
| sogomylittleponey0015412fcc5 |
| sogomylittleponey0015412fcc5_acl |
| sogomylittleponey0015412fcc5_quick |
+-------------------------------+
[/code]

Id of one reappearing event: 31FF-56543600-5-151FFFA0

[code]
select * from sogomylittleponey0012c48149e where c_name like '%31FF-56543600-5-151FFFA0%'\G

1. row
c_name: 31FF-56543600-5-151FFFA0.ics
c_content: BEGIN:VCALENDAR
PRODID:-//Inverse inc./SOGo 2.3.2//EN
VERSION:2.0
BEGIN:VEVENT
UID:31FF-56543600-5-151FFFA0
SUMMARY:Temps partiel
LOCATION:Domicile
DESCRIPTION:Pas disponible
CLASS:PUBLIC
PRIORITY:5
CREATED:20151124T100520Z
DTSTAMP:20151124T100520Z
LAST-MODIFIED:20151124T100520Z
RRULE:FREQ=WEEKLY
DTSTART;VALUE=DATE:20151125
DTEND;VALUE=DATE:20161229
TRANSP:OPAQUE
END:VEVENT
END:VCALENDAR
c_creationdate: 1448359520
c_lastmodified: 1448359520
c_version: 0
c_deleted: NULL
[/code]

I tried to backup/restore all data of the user affected by this problem but it doesn't fix this issue! I don't know what information you need to debug or reproduce this.