This has developed suddenly on two servers connected by a 100Mb connection between buildings.

Log Name:      DFS Replication
Source:        DFSR
Date:          12/11/2022 21:00:25
Event ID:      5014
Task Category: None
Level:         Warning
Keywords:      Classic
User:          N/A
Computer:      DC1.domain.local
Description:
The DFS Replication service is stopping communication with partner DC0 for replication group Domain System Volume due to an error. The service will retry the connection periodically. 
 
Additional Information: 
Error: 9036 (Paused for backup or restore) 
Connection ID: 1FD17D3D-1EB1-4C54-A919-0CB62D200075 
Replication Group ID: 329E9E69-8D98-4557-B2AA-4C3E4455A3C3
Event Xml:

 
   
    5014
    3
    0
    0x80000000000000
   
    1686
    DFS Replication
    DC1.domain.local
   
 
 
    1FD17D3D-1EB1-4C54-A919-0CB62D200075
    DC0
    Domain System Volume
    9036
    Paused for backup or restore
    329E9E69-8D98-4557-B2AA-4C3E4455A3C3
 

If this is happening at the same time every day you can ignore it as it is just for the Windows backup.