Thank you for reaching out the community.
If you are using 4.8.0,please apply 4.8.1 because there are some unresponsive issue on 4.8.0.
For more details, please find following release notes.
Out of 16 OSS, as per your update there are few causing the issues.
So, i suspect the load reached to bottle neck to those OSS servers, where causing these issues.
Moreover, in move there is a concept as..... last connected SVA, so the clients which are connected last MOVE OSS server, so it will connects to those and will try to fall back, only when it is not able to connect the existing one.
In this concept, take an example you have 16 OSS< and one of those always will show 250 active client connections, even though other OSS servers, still not grown more than 100.
By this the load increase will impact, for this... we can disable the last connected OSS option via sva manager through the command, but this would be done only by the service portal case opened with McAfee.
But again, still I'm assuming that is the issue, until it confirmed this is causing... we cant conclude the change mentioned above will resolve.
Go to default queries and reports & search with these 3 queries, you will come to know the load and more info from all these 3 queries to validate by self and see why those many clients reporting to only this SVA.
The query names as below.
MOVE Antivirus SVM Load: Number of Connected Endpoints
MOVE AntiVirus: Clients Connected With a given SVM
MOVE AntiVirus: Clients connected with a given SVM and SVM Manager
Additionally, you have to check the client load is selected as "moderate" which is default setting as per the image attached and also go through KB88997, for more information for the same.