Email duplicated when sent to mail group

I started seeing this issue shortly after upgrading to Domino 8.5.0 from 6.5.4 . We have a few groups that are automatically populated based on an Organizational Structure within Notes. Several users are affected with the duplicate emails even though they only appear in these groups once. I have removed them from the group and they still receive the email, except they will only receive one when they aren’t listed. There is one group nested within these groups and I have verified that they are not listed within this group.

Please see the examples below.

Email #1:

Field Name: $MessageID

Data Type: Text List

Data Length: 75 bytes

Seq Num: 1

Dup Item ID: 0

Field Flags: SUMMARY

OF127746AF.663BEDE2-ON8625768C.006FDB9E-8625768C.00702355@LocalDomain

Field Name: $Orig

Data Type: Response Reference List

Data Length: 18 bytes

Seq Num: 1

Dup Item ID: 0

Field Flags: SUMMARY

F127746AF:663BEDE2-N8625768C:006FDB9E

Email #2:

Field Name: $MessageID

Data Type: Text List

Data Length: 75 bytes

Seq Num: 1

Dup Item ID: 0

Field Flags: SUMMARY

OF127746AF.663BEDE2-ON8625768C.006FDB9E-8625768C.00702363@LocalDomain

Field Name: $Orig

Data Type: Response Reference List

Data Length: 18 bytes

Seq Num: 1

Dup Item ID: 0

Field Flags: SUMMARY

F127746AF:663BEDE2-N8625768C:006FDB9E

12/14/2009 02:25:19 PM Router: Message 00702410, 006FDB9E delivered to

Username\Company

12/14/2009 02:25:38 PM Router: Message 0070352D, 006FDB9E delivered to

Username\Company

I’ve asked our developer to look into this automated process and he can’t find any issues with it and uses it to populate other groups which do not have this issue.

Any any ideas would be greatly appreciated.

Thanks