Mysterious roster changes

From time to time I experience “spontaneous” changes within the rosters of my users.

Among my custom plugins, only one of them makes any changes to roster and it can only set the subscription status of a pair of users to “both”. Sometimes, these “both” values are set to “none” and I have no idea which process could cause that. Have you experienced anything like that in the past and what could be the reason for these unvoluntary roster changes?

Thanks!
openfire.txt.zip (989 Bytes)
openfire.script.zip (2826 Bytes)
openfire.log.zip (214 Bytes)
debug.log.zip (3972 Bytes)