Openfire Offline Message table is growing

Hi,

my Offline Messages are growing day by day and i have no idea why.

currently my ofOffline table counts 501801 rows with 2,2GB Space used.

i cant open the Offline config in the webgui anymore, because it tries to calculate the used offline space, which takes ages.

this my my offline config:

this problem is bugging me for quite some time now and the only solution so far seems to purge the offline table every few weeks, with the danger of loosing offlinemessages the users expect to be delivered.

im currently using Openfire 3.10.3 oracle java 1.7.80 and i had this problem since some 3.8.x version, but im not sure when it started exactly.

is there some way to find out whats causing this?

greetings