samba - Jan 2018 - ERROR: Duplicate link values for attribute 'member'

I updated two AD DCs from version 4.6.12 to 4.7.4. Before the update, 
both "samba-tool dbcheck" and "samba-tool --cross-ncs" gave
no errors.
After updating, all seems well, including replication, except for this 
error when running the above commands (private info sanitized):

ERROR: Duplicate link values for attribute 'member' in 
'CN=GroupName,OU=MyOU1,OU=MyOU2,DC=MyDomain,DC=com'
Duplicate link 
'<GUID=0bed128a-263d-4a0e-970a-706e8a72b039>;<RMD_ADDTIME=131583343650000000>;<RMD_CHANGETIME=131583343650000000>;<RMD_FLAGS=1>;<RMD_INVOCID=26ee09a9-c036-4e6c-b2fa-a7f5bd73e84d>;<RMD_LOCAL_USN=471122>;<RMD_ORIGINATING_USN=471122>;<RMD_VERSION=1>;<SID=S-1-5-21-xxxxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxx>;CN=MyUser,OU=MyOU1,OU=MyOU2,DC=MyDomain,DC=com'
Correct   link 
'<GUID=0bed128a-263d-4a0e-970a-706e8a72b039>;<RMD_ADDTIME=131583343650000000>;<RMD_CHANGETIME=131583343650000000>;<RMD_FLAGS=1>;<RMD_INVOCID=26ee09a9-c036-4e6c-b2fa-a7f5bd73e84d>;<RMD_LOCAL_USN=471122>;<RMD_ORIGINATING_USN=471122>;<RMD_VERSION=1>;<SID=S-1-5-21-xxxxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxx>;CN=MyUser,OU=MyOU1,OU=MyOU2,DC=MyDomain,DC=com'
Not removing duplicate links in attribute 'member'
Please use --fix to fix these errors

When I run --fix with either "samba-tool dbcheck" and "samba-tool
--cross-ncs", the output is the following:

ERROR: Failed to fix duplicate links in attribute 'member' : (68, 
'samldb: member CN=MyUser,OU=MyOU1,OU=MyOU2,DC=MyDomain,DC=com already 
set via primaryGroupID 1203')

So, the error persists and seems impossible to fix using the common method.
As I said before, replication is working without errors. Any ideas?

Thank you.